Horse Cooties

Story by iplank on SoFurry

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Like most get-rich-quick schemes, this one was bound to backfire in some way. Telah's spell worked perfectly- just on the wrong target- and now it is a race against time before the entire household becomes equine!


(FtM tf Stallion, M tf Hinny, F tf Jennet)

Telah was a skilled Mage when it came to enhancements- making a person faster, stronger, more resistant to illness, and other such spells. That was where her studies started anyway. Eventually her studies lead her to spells to transform into other creatures, or create original alterations to bodies, to enable people to do things they were completely unable to before, or to hide in plain sight. When she heard whispers of an organisation called RHE that was using magic to enable people to make specialty food, she immediately looked into it. It all seemed to trace back to the infamous Dr. Hemlock from bygone ages, who created a man who could digest almost any old garbage, produce protein rich semen, and then they were able to filter the proteins from that to make food- using the man as a filter. Basically it enabled her to turn almost literal garbage into edible food. Telah is a good spell caster though, what was stopping her from doing the same? She could make a fortune making meal replacement drinks, how hard could it be? Well, at least harder than she initially assumed, she quickly found out.

Telah and her husband Marcus moved out to his sister Ren's ranch just outside the city. It had been a ranch, at one point anyway. The only animals she kept there was a single goat for milk, and her older pet dog; Gospel. She did not have time to maintain a full fleet of critters after she inherited the land, but she did tend the place and it was a nice quiet place to live. The barns that used to house the animals though were all empty- so Telah could use them for whatever she wanted, as long as she didn't blow the damn place up with her spells. Her idea was that she could take a fertile animal, super enhance its endowments and then collect its semen to convert. A horse can survive off just grass and grains with the occasional apple or carrot. Or a sugar cube if you really wanted to treat it. The point is- it wasn't particularly expensive to feed.

The more Telah experimented the more complications she found. First of all, a lot of endowment spells did not increase semen production because it was more of a magnification spell- the equipment still operated the same as it did when it was small, everything just seemed bigger. Then there was the issue of being able to transmute the semen into a palatable drink. She could do it with spells, but was unfamiliar, and ultimately decided it was more practical to turn to alchemy. If she had to learn how to do it from scratch regardless it made more sense to go with the method that did not consume mana, which she needed for other parts of the process already. She managed to convince Marcus to help her with that part. With the mana she would save avoiding that, she looked into perhaps making a spell that summoned semen. If you can make water or fire from mana, semen should be possible too. It would be far too complicated though as she found out- but Telah did find a solution. She can use spells to multiply semen the creature already produced, creating bucketloads from what would have been a single drop. Being out in the sticks, there are no other spellslingers anywhere near them, so there was a mana surplus. Next, to create the endowments she overlapped several equine transformation spells, emphasizing its genitals only, on top of a standard endowment spell. Because there was no need of actual sperm to impregnate anything, she also isolated the prostate transformation part of a male horse spell and looped it where the testicles would have transformed. This should- if she is correct- convert its balls into more prostates, greatly increasing its capacity for sexual fluids, robbing it only of its ability to reproduce. Now she only needed to wait for Ren to find them a stud to buy to apply the spell to.

The next day however, Telah found Ren in the barn, looking over her notes. "What's up? Looking for a spell for something?"

Ren looked at her and motioned to the huge old book. "I was thinking, if we are looking for pure profit here- we already have a farm animal. Already milk the goat for... well, milk. We could transform the goat into a stallion. But I can't find any mention of turning an animal into another animal, just human to animal. I know it must exist because your layering these equine features onto something that was already a horse."

"Its universal- it says human because it assumes the caster is human if they are reading a book on magic, but the spell has the same effect on anything living. You could turn a plant into a horse- it would just be so stupid it would die because it doesn't know enough to breath on its own. The spell expands what the living creature already has through mass condensation and elemental transmutation- all matter can be broken down into energy as the most basic form; thus all energy can be rebuilt into matter. So the farther the creature is from the target transformation the more mana will be consumed to make the spell happen, but with enough power it will work on literally anything organic."

"Well heck, lets go stud a goat." Ren went to lift the huge tome but underestimated how much it weighed and ended up sliding it off the edge of the table instead of lifting it- unintentionally knocking off a quartz prism.

Telah seen it fall but also realized it would hit the ground before she was able to dive into it and catch it, so she used a spell to halt its position in the air. Ren apologised, blushing that she had trouble lifting the tome. Telah scooped the quartz out of the air and felt a powerful jolt into her body through her arm!

"Uh oh."

"What? What is that quartz for?"

"Its my spell. It is complicated so to avoid screwing it up casting it off the top of my head, I pre-cast the spell and trapped it in the crystal. Quartz not only conducts charges of energy- it resonates at very regular intervals. So you can use quartz to regulate energy flow. Ever hear of a quartz watch? Yea- its so regular you can keep time with it too."

"Yea but why the 'uh oh' then? It didn't hit the ground."

"I used a spell to stop it... I think the mana flowing through it might have triggered my spell."

"But... you're still human."

"Uh... yea. Guess it's fine then. Let's hold off on converting your goat though. A goat is supposed to be a goat- it would be best if we can do this on something that was already horse so we don't have to worry about turning it back."

Ren raised an eyebrow. "You... don't have a counterspell for this, do you?"

Telah laughed nervously. "N-no. So if we do need to use your goat, you might want to wait for me to figure out how to undo the spell first. Otherwise it would be trapped forever."

Telah was a bit nervous about the spell, but told Ren it was fine so she did not also worry. Even if it was triggered it wouldn't turn her into a horse because only a minuscule fraction of the required mana passed through the crystal... but if it activated, the spell would continue to draw in ambient mana. She would still turn into a super horse- just slowly. For this reason, she went to work looking into a possible reversal. Since the transformation was custom, she also needed a custom reversal spell to cure it. Without a horse still, she had no guinnea pig to test anything on. Telah ended up having to help Marcus most of the day anyway, still figuring out the transmutation alchemy for the semen. Telah had 'harvested' some semen from Marcus himself to run the experiments on. It was going well- they had mastered the flavouring part anyway. Alchemy basics was all about destilling the essences of things and transferring them to other things. Once the essence of something's flavour was pulled, the sample could be used to convert something else of equal mass into it. So they could steal the flavour of a berry, turn a vat of water into berry juice, and then use the juice to convert the semen. Between working in the barn and helping Marcus- Telah's legs were sore from never actually sitting down all day.

Telah's leg muscles felt really tight by the evening and she decided to turn in early. Most of the setup for her schemes was done and they did not even have the animal yet- so she could afford to take things easier. She had a shower and noted her clit was poking out, looking rather engorged. She felt herself rather gingerly, feeling she was quite sensitive. Was something up, or was she just psyching herself out? She flopped down in bed and went to sleep, long before Marcus went to bed. She had a strange dream where she was speaking to Ren in the barn again. Their words were a jumble of nonesense but they both understood each other in the dream. Telah found herself thinking several times how pretty Ren is. She was Marcus's sister after all, so if Telah liked Marcus enough to marry him- Ren isn't too far off. She never thought about it before though, so it was odd that she would now suddenly. Ren's looks were almost distractingly good. Without having seen the horse, or speaking of it at all, Telah suddenly bolted at full speed into the fields and seen a mare running from them. It was the wrong gender, but still a horse which means still useful. In the dream, Telah was able to slowly start to catch up to the horse even though it was running full blast. She even tripped at some point but was still able to continue on all fours at the same speed! In real life, her leg muscles twitched in her sleep and her thighs swelled bigger and bulkier with muscle, which caused her butt to swell a bit rounder as well. In her dream Telah felt oddly giddy, focussing on the mare's butt more than anything- since it was mostly what she seen chasing it from behind. Bit, round butt, firm with muscle. In real life her vaginal passage started to clench gently, shrinking a bit each time. Her pussy became increasingly small, but her clit continued to swell and throb more aggressively. In Telah's dream the mare suddenly stopped as her clit popped out and her pussy winked. Telah was not at all ready for the sudden stop and tried to stand back up to rear up and stop herself, but slammed crotch first into the mare, flopping over her back. Wait, why was the mare small enough for her to bend over? The huge firm rump pressed into her crotch fit oddly well, its warmth pressed into her felt so nice. In reality she was starting to hump the bed gently. In the dream the base of the mare's tail was poking into her crotch a bit irritatingly. In reality, it wasn't a tail poking into her, it was something poking out- her clit now distended from its hood considerably bigger than it should be was jammed into the bed with each rock of her hip.

Telah woke up the next day feeling a bit off. Even though she went to bed early, she woke up late and Marcus was already out and about. As soon as Telah sat on the edge of the bed to rub the sleep from her eyes she noticed- her genitals had changed! Her clitoral hood had grown along with her clit, becoming the foreskin on her clit which was now a small penis! Her labia had stretched out and been filled with testicles that had formerly been her ovaries and were fused together into a scrotum at the front, but still divided at the rear around what used to be her vagina. The opening was small, and also shallow- it no longer lead to a womb, it went an inch into her and then came to a dead-end. She was technically a He now. Telah's heart raced- now she knew her spell got fired into her own body. She was going to get turned into a hyper horse if she did not find a cure! She also remembered her strange dreams though and bit her lower lip. She gently touched her small penis feeling the stiffness spread into it. She sort of wondered what it would be like to have a penis. She sort of wondered what it would be like... to have a horses. The spell would be working slow, so she presumably had a lot of time to figure out a reversal spell- how hard could it be? Maybe... she could just let it do its thing for a bit.

Telah started to stroke the small penis, feeling the stiffness seem to backfire back into her after it had filled the shaft. The piping stiffening caused it to straighten, pulling farther back in her torso- rerouting from where her pussy had been to her butt, where her transforming G spot became a prostate. This caused the already uselessly tiny pussy to shrink the rest of the way- the passage collapsing and vanishing entirely as the remnants of the labia fully fused into a scrotum so her balls could hang lower as they slowly grew from the size of grapes to the size of chicken eggs. Her penis had been so small to start that she could only use three fingers and a thumb because its all she could fit on the shaft, but as she pounded it, it swelled in size. Soon she could use all her fingers, then she could actually grip the shaft. It became as big as Marcus' own shaft, and as it stretched still bigger- the thought of having a bigger dick than her own husband sent her over the edge and straight into her first male orgasm!

Telah got dressed after and was planning to act like everything was normal. She had to turn down helping Marcus again today, because she had to work on the reversal spell. Luckily thanks to yesterday's conversations he did not suspect anything because of her working on an undo button already. Ren was already in the barn looking over some notes, seeing if she could help jump start the effort as well and Telah gladly accepted the help. As time wore on though, Telah started to wonder if this had been such a good idea. She kept remembering her dream, and glancing over Ren's figure. Because her butt was bigger, her pants did not fit properly, which pulled the fabric tight. Her erecting dick pressed into the taught fabric and rubbed against it, which then caused her hips to twitch every now and then, trying to hump before she catches herself and stops! She eventually had to make up a flimsy excuse that she works better alone to shoo Ren away before her rock hard erection wore a hole straight through the front of her pants from having Ren around. She couldn't think straight like this- every subtle movement of her legs or hips caused her dick to rub against its taught prison. Once Ren was back in the house, Telah went deeper into the barn and sat down to pull her pants down a bit and let her junk flop out. It looked slightly bigger than it did this morning! Telah immediately grabbed it and started to beat off. Her balls flopped over the front of the stool, her taint throbbing against the hard seat. More and more shaft started to expose itself over the top of her grip. Her balls swung with more weight against her scrotum as they grew! Her using her genitals like this was stimulating the flow of mana- speeding up the changes most likely. But she can't think straight with an erection like that, so she was trying to race her changes. She needed to get off as quickly as she could to avoid more changes, but still relieve herself. Her heart raced faster, half in arousal and half in panic as the cock grew still bigger. It was larger than any human member she had personally seen and very thick too. Some of the fat veins that rolled around just under the surface were almost as thick as her pinky fingers. There was what felt like a muscle rib at the center of the shaft that was swelling bigger and becoming unusually sensitive but she realized it was probably the medial ring forming- the point where the shaft folded in on itself when it became dormant. An equine phallus is most sensitive on the glans and the medial ring- you won't get a horse off just polishing its shaft. Some grey spots were forming on the skin and her scrotum was darkening to grey as well, starting to take the coloration of horse genitals- there are horses with pure pink dicks, but they are basically albinos. As she reached climax again, the glans of her cock swelled very big- but it was still human shaped, which made it seem way too big for the shaft it was attached to. The volume of her cum was massive this time, well beyond a human load. She grinned at herself, knowing it would only get bigger. Once her other modifications started to kick in, she would be able to produce.... wait, no. She shouldn't be waiting for it to progress that far- she shouldn't want these changes! She managed to stuff her half human monster into a pant leg and zip back up, returning to work on a reversal spell. She still was not in a particular hurry, and even stopped to double check work on the actual spell when she crossed some relevant information in the tome and got a bit side tracked.

During dinner Telah struggled to make it seem like everything was normal. She was unusually quiet and struggled against her own thoughts. On the surface she looked absorbed in thought which she passed off to the others as just thinking about possible routes for the reversal spell. Under the table though, her dick head was getting squeezed by the curve of the fabric at her knees! Being by her husband and his pretty sister, her cock was throbbing so hard it felt like her heart was in her crotch. By the time they finished eating she had to scurry off in a hurry- having heard several teeth on the zipper of her pants pop open from tension after few minutes toward the end of dinner. Luckily she was wearing working jeans so she doubted her body was physically even able to create enough outward force to rip the button off- but the zipper was forced almost fully down by now, which exposed the base of her bent cock to open air. She was practically hobbling to the bedroom upstairs to get to the shower, to desperately try and subdue her genitals with ice cold water. Her balls occupied so much space she was afraid to walk normally at risk of crushing them between her legs. She just tossed her clothes onto the floor to rush into the shower, she did not turn the warm water on at all, only the cold. Telah yelped at the feeling as she got into the frigid shower but grit her teeth and bared it, knowing cold was the bane of arousal. Her scrotum pulled tight almost immediately, hugging her large balls to her body to protect them. When it did though, the skin shifted further, expanding from the tension the retreating balls created and the new skin pooled at the base of the shaft, becoming a shallow sheath. The internal heat throbbing in the cock did not die so easily though- the coursing blood feeding it kept it hot even under the cold water. Most of her blood pressure was hammering toward her cock, so she was more likely to freeze the entire rest of her body than she was her dick. Her nipples tingled with how tight they became from the cold water, and water started to bead on the surface of her breasts- the pours having grown too taught to accept any liquid. Telah faced into the water stream and took a step back- so rather than land on her head and pour down, the stream hit her crotch directly. The weight of the water droplets stimulated the shaft, causing it to buck and throw beads of water back into the air, then wobble back down in place before bucking again! She groaned in frustration and arousal. Telah unthinkingly angled her hip forward, which put her dick at more of an upward angle, which caused the water streams to hit the glans directly, causing them to tighten and swell in pleasure as the cock continued to buck! Now at the upward angle, when her dick throbbed it thudded against her ribs- slamming its way through her cleavage, making her tits jiggle violently as it slammed in, then fell back out as it loosened, then slammed back again. Hitting the dick against the torso was how a horse masturbated! Because a horse doesn't have hands- but it does still masturbate. The fact it made it to her cleavage however meant it was at least a few inches longer than before. And which each thud it got a little bit deeper in, a little bit bigger. Her scrotum darkened more and more, turning from grey-pink to bruise purple to completely smooth, glossy black. The sheath swelled fatter and grew deeper into the void left by her non existant pussy. The medial ring swelled larger, becoming outwardly visible now. The huge veins throbbed in time with her heart beat while the shaft throbbed with her pleasure, beating itself against her chest making wet, hollow thuds, causing her heart to jump a bit with each hit. She had her eyes closed and face to the roof, leaned against the back of the shower. It was like her cock had taken over entirely- Telah wasn't doing a damn thing, she just stood there while her dick took care of itself. Her balls started to swing a little and sink from her torso now, growing too large to be held up for any length of time. The glans of her dick engorged almost painfully, tingling and almost itching from internal blood pressure. The corona stretched farther out, pulling he helmet shaped human glans outward into the more gentle dome of equine phallus. The divot of the urethra sunk in very deep as the glans hardened further like hard, unrelenting rubber, and then the urethra itself projected outward, rising from the pit around it like a tiny pipe. The glans became gigantically flared- catching even more of the water streams directly on it, increasing the pleasure and acting like an open umbrella for the rest of the dick. Her heart hammered even faster than the cock, but it had grown so large now that when it swung back it flicked water into her face! The head was level with her mouth! It was like it was demanding her to taste it! She opened her eyes a moment, looking at her huge flared glans eclipsing her cleavage from her view; the pink flesh having turned a soft violet from blood pressure. Telah opened her mouth and took in the edge, nibbling on the corona, but it only took that brief moment for her to absolutely explode. The stream of cum slammed against the roof hard enough to scatter sticky strands around the shower. You could audibly hear the stream of cum thud against the roof, five times before the strength of the shots became too weak to touch the roof.

Telah looked at her feet as she slumped down on the bottom of the shower to catch her breath. She could no longer move her toes individually- they had fused at the base when she was unintentionally masturbating. Her toenails were thick and black. Her changes seemed to be getting faster! Her dick went soft quickly enough, but took its sweet time packing itself away. Telah winced as a dull ache inhabited her balls and she could feel them shuffling around a bit on their own. They must be converting to prostates already. Which was bad- if that transformation was happening already that would mean she would need to cum three times in one sitting to empty out, and eventually her multiplication spell on the cum would make it so there was almost no downtime on all three- so between the three of them, if stimulation remained continuous, she would literally never stop cumming. She gently touched her balls and could feel the squirming under the surface as they changed. The dull ache was sort of like the aftershock of getting kicked in the nuts, but faded in and out. Soon it was joined with a warmer feeling, a tingle of pleasure and before her huge dong even fully packed itself away, it started to slide back out again. The pain was turning to pleasure- her body thought the alteration of the balls was a threat at first but once enough became changed the body welcomed it in. Once a transformation is far enough along the original form becomes the oddity and is shoved out. She heard Marcus through the door flop down on the bed. Even if she wasn't in immediate trouble, Telah doubted she could somehow keep her fully equine package hidden anymore.

Marcus was slipping his clothes off and did not even look over when Telah came out of the bathroom. His back was to her sitting on the edge of the bed facing the wide window that overlooked the fields.

She spoke to him in a honeyed tone. "Marc... I have been feeling the itch.... wanna help a woman out, hmmm~ ?"

Marcus smiled and was going to put his legs up on the bed and look at her but she flopped down on the bed hard, causing the mattress to suddenly sink in, yanking him toward the middle of the bed. Marcus and Telah bumped each other in the middle, and her huge horse cock flopped over across his lap. They were both surprised, but Telah recovered quicker and tried to look as calm and collected as possible.

"Soooo, your sister accidentally made me fire my own spell into myself...."

He just gawked at it, dumbfounded. His own half erection was about a tenth of its size, at absolute best. He put a hand on it and could feel her heart beat in the fat veins as he traced the dark flesh to her crotch. Yea, it was definitely real.

"Do you still have...?"

"A pussy? No. I also don't have the reversal spell made yet to fix this, I have an idea, but I need to tame this thing first."

Marcus was not bisexual, but the beast was attached to his lovely wife and that was all his own dick needed to know to rise to the occasion. The dick was so huge he did not know how to even handle her rod as it became fully erect again itself. Even the entire length of his arms could not completely cover its length from tip to base, but Telah instructed him to only focus on the medial ring and head. She would not have problems getting off anyway- her balls were periodically sending sudden sharp spikes of pleasure as their changes to giant prostates approached completion. Marcus pushed her to the side, rolling Telah onto her back and then rolled ontop of her. His balls were so small compared to hers that they fit in the cleft of her scrotum. He pressed his human dick into the bulge of the huge equine urethra on her ebon meat pillar and thrust the two dicks together, while grabbing her beast just under the head. He used his thumbs to rub the underside of the corona, causing it to flare from the feeling immediately. Talah nibbled the other side of the lumpy rim and her boobs jiggled their soft curves against the shaft below his hands.

Telah quickly pushed her shaft up toward him as she rocketed to her peak. "Marc, quick, suck!"

He was not sure about that, but she practically shoved the head into his mouth herself. Or as much as could fit anyway. it was too big- especially when already flared- to fit into a human mouth, but she only really needed to get her urethra into his mouth. The cum blasted with enough force that he basically had to swallow, because Telah wasn't going to remove her dick till the orgasm ended and there was a lot more than he could fit in his mouth at once. Telah was worried she would still feel backed up even after the second orgasm but she actually felt fine. She flinched as there was a strong but short lived pain in her balls again, and she touched them, pushing in just a bit to test. They were still testicles- the nearly complete transformation on them had reversed itself. Marcus thought he was dizzy from lack of air being force fed such a long orgasm, but his head was spinning for other reasons. He was very dizzy and horny and his dick started to fire jolts of pleasure off like an orgasm, but only for a moment at a time. He grunted and groaned as he got onto all fours on the bed, too dizzy to focus his sight on anything to see with each surge of pleasure his dick swelled. His prostate filled to capacity almost instantly and the overflow backed up into his nuts. All the chords trailing to his testicles inside the scrotum became rock hard from backed up fluid and his balls swelled alarmingly fast. His scrotum quickly started to darken and pull smooth, desperately trying to keep up with its contents. His dick was stuck at full diamond hard and pratically vibrated with the growth stuffing itself into the shaft. It came in such large bursts it almost looked like another, larger penis was growing up inside of his own shaft, and then another, and then another. Each wave increasing the girth and length of his shaft and changing it in surges, turning it equine as well! It reached past his belly button, then his lower chest, then his collar bone and stopped at his neck in length- so it was neither as thick nor quite as long as Telah's. When the head stretched out, deforming its human shape into a proper equine appearance Marcus fell back on his butt and came explosively almost straight up into the air.

He flopped back onto the bed on his side, looking at his horse cock in shock. "W...what happened to me?"

Telah bit her lip nervously. "W-well, my theory worked."

"What theory? That you gave me your horse cooties?"

Telah snorted in laughter. "Yea, basically. Like most things, mana takes the point of least resistance, so the more flow gathered toward my body the faster it could go, because the path was already predetermined. So, my changes were speeding up, and the farther they went the faster it became. So I discharged my mana into you."

"Oh great, so now we will both become hyper stallions?!"

"W-well no. The spell is on me, not you. Mana isn't being pulled into you, I had to force mine into you. But with the flow of mana removed from me, the speed of my changes basically reset to zero, and it was almost a full day before anything even started to happen."

"But, the spell is still working?"

"Yea... I definitely still need to make that counter spell."

The two of them went to sleep pretty quickly after that, exhausted from the pleasure and physically worn out from the changes. At breakfast Marcus broke the news to his sister, and feeling to blame for the whole mess, Ren offered to help Telah find the counter. Telah quickly declined, telling Ren she was just not used to working with others and having another chef in the kitchen might distract her. In truth, she declined so quickly because there was no way she could keep her erection down with Ren standing there. And her package was already too big for her to close her pants. The button and zipper both had to be left undone in order to fit her pants on, so if she popped a boner it would be waving around in open air. Telah went to work on her studies in the barn, but found herself flinching and shuffling her feet as dull aches throbbed in her balls as they shuffled around themselves. She discharged her mana before the change completed, causing her body to reject them and revert to regular horse balls- the last platou of the changes that actually completed. That means now the first changes that rev up are going to be her balls changing all over again. The aches were actually easier to deal with, it became harder the more toward the side of pleasure the pulses got. When the ache hit, it was a pain that then faded and she continued reading. When it was pleasure that hit, it left a tinge of arousal and caused her shaft to fatten up in her sheath. Soon it started to cause her thoughts to wander and it was hard to concentrate. Her dick emerged on its own in a lazy arch from her pants. She had to stand back from the book a bit so her dick didn't make contact with the table. Telah tried her best to stay on course and find her cure, but the pleasure jolts became too strong, finally causing her to thrust involuntarily so hard she almost toppled herself over! Her balls swelled a bit in their scrotum as the changes completed and suddenly she was flooded with even more arousal and she felt like it had been a year since she last blew her load. She now effectively had three prostates, so while one was still empty, there was two that were full, which is still twice the maximum capacity any normal creature has.

She had no choice, she went to the stood near the back of the barn and masturbated. She could practically hear the liquid gurgling in her mutated balls as they bobbed up and down on their own, plopping down heavily in the scrotum- which also pulled the scrotal flesh taught, which tugged on her sheath and sent tiny tremors up her shaft. When she climaxed she exploded even more cum than ever before- ropes of hot goo as thick as her thumb splashing the barn floor. Telah's feet were cramping and started to shift. The bone clicked and compressed as her ankles stretched away from the toes, and her toenails started to get even thicker and started to overflow the toes. Her dick did not soften at all. She had still only emptied two prostates... she still had one full tank. The more she masturbated though, the faster her changes were going to speed up, because she isn't supposed to have a dick at all- so using said dick is encouraging the change. But if she can't concentrate enough to make a counterspell then the changes will take her anyway- just much slower. Needing to hurry, Telah placed one hand just over her medial ring so she could push on it with her strokes and then lifted her rump to penetrate herself with two fingers- going for her original prostate. She could have gone for her balls, but if they turned out to not be 100% changed yet she would hurt herself. Her devolving feet touched the ground in spite of the tall stool- her ankles now far from the ends of her feet. She could feel the rectal muscles changing, the sphincter transforming to be more efficient. A horse butt is actually quite good at keeping itself clean- two rings of muscle to create an almost airlock zone with a third ring of muscle that pushes contents out to clean it. Scientists have actually mimicked the design of a horse butt to make self-cleaning nozzles on industrial equipment. Of course its changes also caused the opening to enlarge, the anus inflating in size to a plush ring; now connected to her balls by a pure black taint. She managed to climax quickly again- never letting the pleasure fall too far from her last peak. When she finished making another large puddle of love on the floor, her beast finally started to go soft again, flopping down and then slowly inching back toward her body to fold in to the sheath. Telah examined her feet- now large hooves. She had some fine fur just over the hoof but no where else yet, it only trailed an inch up. Some grey splotches of skin appeared around her sheath though- the start of the black flesh spreading. Telah immediately rushed to her tome to resume studies while she had the chance. The magic was going to shorten her refractory period as much as it could.

She managed to get what reversal spells she could pre-made, which was as far as the actual research could take her. From there on she needed to basically mash them together like she did the transformation spells- just inverted. It sounds more simple than it is. It took her over a week of working to make her custom spell and imprint it in quartz in the first place, now she had to do that again to cure herself- except she definitely would not last a week. As soon as she got back in the house for dinner she was struggling to play off an erection that actually thudded against the bottom of the table- she managed to convince the others she bumped the table with her knee. She had to wait till Ren had her back turned to slip away from the table afterward, as her giant cock slid from under the table and stood up fully erect. It was so large that when it stood in full erection it was basically infront of Telah's face, making it sort of impossible to not see. Telah grabbed Marcus by the hand and quickly dragged him to the bedroom with her. Not completely sold on the taste from last time, Marc was willing to take it from behind this time. Every time they have sex Marcus will become more horse, but it bought them more time spreading the changes out. And Marcus never thought of it before- but seeing his wife with a huge member was pretty hot. She took him on his back, so he could still watch her boobs bounce around vigorously every time she thrust in. It did not take long at all for her to reach climax- horses are not known for their sexual stamina, but she remained hard and thus had to go a second round so she never pulled out, stopping only to catch their breath. Keeping her pleasure at such a high level though spurred more changes.

Her leg muscles bulked up further, becoming a bit veiny toward her crotch. Her hips jostled around with hollow pops as they expanded gigantically, making her lower body drastically larger than her upper body. Her ass became so massive and round with taught tissue and muscle that if she sat down on him, she could probably fit Marcus' entire body between her butt cheeks. Her tail bone started to sprout hairs even before it started to grow out, so by the time the short nub of a tail grew in, the hair was already all the full lush length of a complete horse tail- though softer than a normal horses tail, mirroring the hair on her head. She thought she felt her hands starting to shift as well but she reached climax the second time before her hands changed at all. Marcus started to change before she even hit her first climax but it was almost too subtle to notice, then when she came into him his changes exploded suddenly. With the first climax his legs transformed their shape, giving him hooves as well but the muscle structure did not bulk up and his hips did not change. His tail grew in but had no hair at all- till the second climax. His tail grew out lush and long just like Telah, but a pressure also burst into his neck from his back. He grunt from the feeling as the veins in his neck bulged and his neck started to throb a bit thicker till finally his neck vertebrae popped apart. From the vertebrae above and below the gap, a jelly of calcium dust quickly burst and then condensed into a new vertebrae segment to fill the gap and cover the exposed nerves before any harm could come to them. The first pop happened and the change paused, but after a moment several more went off in rapid fire, lengthening his neck considerably! With a few last throbs, his head became dizzy a moment from increased blood pressure as his neck thickened even more. His final change came more gently as he caught his breath from his changing neck- his hair line advanced down his neck to form a mane. Telah explained that since he was only changing because of discharged mana from her- he wasn't going to change as much as she was, even worse case scenario. His balls would stay just normal balls, he wasn't going to have a berserk libido.

A while later, Telah fell asleep having exhausted herself plowing her husband. Marcus went downstairs to tell his sister the situation was quickly worsening- which she could tell even though he was dressed from his inhumanly large neck and his hooves clacking on the wood floor. Ren suggested that they stay indoors tomorrow. Telah could not keep her beast tamed for very long, so her research was staggered and sloppy and it was only going to get worse. Ren would take her place and try to put together a reversal spell. She was not nearly as good with magic as Telah, but at least she had full control of her mind. To avoid them triggering her, she recommended Marcus lock himself into the basement, and Ren will lock the front door so they will be divided. Telah's mana magnetism was nearly impossible to balance properly. Touching her horse parts sped up the changes, but can clear her thoughts. Firing off into Marcus can cause the speed up of the changes to reset completely- but the sexual contact itself speeds it up. Telah leaned on being able to shave off excess onto Marcus as if it were a solution, but in reality Ren doubted she was slowing the changes at all ultimately. Even with Ren on the case, it was still a race against the clock, because if Telah went full horse Ren would have no one to check her work if she got stumped.

Telah woke up slowly that day- slow enough that she was unable to bother with her morning wood, hovering a half inch off her torso from how turgid it is. The transformation was powered on absorbed mana so while it tired her body out it did not deplete its resources. Her multiple sexual activities are to blame for her exhaustion. By the time she could force her eyes open, her beast was already sinking into the sheath enough that its head was below her breasts again. She just stared at it, marveling at her unintentional masterpiece. So far her spell seems to work just fine, so technically it was a success... it just hit the wrong target. There was something about equine phallus that seemed so alluring- though perhaps it was just the spell tampering with her thoughts. She always knew what it looked like, but had never been in a situation where she would see one so up close and personal. It seemed sort of ironic that humans are almost entirely hairless but have hairy balls, where a horse who is covered in fur has nude balls. There was hair on a horse's scrotum, but it was barely noticeable peach fuz. Even fully erect the shaft had subtle rings on the skin where it folded back on itself when resting. So absorbed in examining every single bump and pour on the member, Telah noticed too late that it was returning to erection and the head gently nudged her breasts from below, demanding to be let into her cleavage. Telah groaned and rolled off the side of the bed, flicking her tail beside her as she did. She would try to braid her long tail to get her mind off her huge member. In the basement Marcus was fairing much easier. He certainly took his time examining his new bits too once he was locked away in the lower level of the house, but when he was done exploring his erection went away on its own. He did almost crack his head on several doorways though- not used to being so tall. Both his elevated ankles due to his hooves and his inhumanly large neck made him considerably taller than before.

Ren was having a hell of a time trying to figure out how to unravel the spell Telah put together. Thanks to her being barely able to concentrate, the reversal spell she had started to put together didn't even make any sense to Ren- only Telah could decipher her own notes. She layered several similar equines transformation spells together, plus fertility spells to make its libido nuts, plus the multiplication spell to give it impossible volume. Just figuring out what animals she used took a long time- she cannot layer more than one horse transformation spell- casting the same spell on the same target will have no effect at all. So she used sub species- different enough that they are considered new transformations, but still so similar to horse that you aren't creating some jumbled mess of a creature by blending them together. That also made them hard to distinguish when all you had to go by was the spell runes themselves.

Ren was still no where to be seen by dinner time, still toiling away by lantern light. Telah was staring at the roof, her mind absolutely blank, desperately trying not to think of anything sexual. Her side of the bed was sopping wet from all the precum streaming from her rigid cock, vibrating in between her wrists were she held it. She no longer had hands- she watched them devolve as she used them to try to hold her dick from slapping into her cleavage to masturbate itself again. Her body changed them as if doing it to hinder her ability to stop it, but she still managed to hold the dick still between her equine wrists. Since she had not moved her limbs around much since then, she had some lingering phantom feelings- like her fingers were still there under the skin somehow even though they had fused into a single bone. Telah was naked now around the clock- she might be able to get a shirt on but if that was the only thing she could put on it sort of seemed pointless infront of everything she could not cover. Every small sound caught her attention- anything that was not another horny thought. It was because of that, that Telah noticed her ears changing right away. They started to flick in the direction of sounds to hear them better automatically, becoming longer and leaf shaped, but thinner than they were as a human, so they did not actually change mass. She felt a slight itch on the back of her neck against the pillows every now and then as two or three long hairs would sprout, causing her hair line to advance down very, very slowly. Her hips kept trying to buck involuntarily, and every time they did a full globule of precum fired out of her dick, looking like a mini orgasm. The veins throbbed powerfully constantly, and there was a thin stream of pre connecting the head to her chest constantly. She looked at the corner of the roof and wall because lowering her eyes any more than that filled her vision with cock- the head was level with her face when she wasn't holding it back. She was breathing heavily, trying to settle herself down but afraid of actually trying to think of anything at risk of thinking of the wrong thing. Her ears flicked at the sound of movement from downstairs and the moment Marcus's semi equine appearance flickered in her imagination she yelled out in surprise and bucked forward and locked in that position as her cock exploded against the wall. There was so much cum it soaked the entire head of the bed, her entire upper body, her face and there was still enough to run off the side of the bed onto the floor. Her hair was mostly safe thankfully because she was laying on top of it. As she screamed her pleasure, the muscles in her chest tightened and bulked up, the growht travelling down her arms and to her abs as well making her look quite muscular. Every time she took a sharp breath between yells her nostrils grew a bit bigger to take in her masculine scent. Even once she finished her orgasm the stream continued a bit and then tapered off, back into the near constant flow of precum. It was hard to tell precum from her actual ejaculation- testicles add the sperm and turn the liquid white, but she has three prostates and no testicles so the fluid is never turned white, its all clear.

She was still just as horny! She only emptied ONE of her three prostates! It would have been better to empty one of the ones in her scrotum because the original one can overflow into them, but they cannot overflow into her original; the flow is one-way only. She sat up, putting her legs over the side of the bed and aiming her flesh cannon at the window while leaning back on the bed, trying to use its weight to hold it away from herself without actually touching it. She grunt softly, rocking her hip a bit. Her plush, projected equine anus felt good pressed into the soft bed. The pre started to spurt in greater volume more regularly. The bridge of her nose started to widen with her larger breaths and she could feel a strange subdued tingling in her teeth as the front teeth started to grow in size, making her mouth feel cramped and putting pressure on her jaws.

"Huuh..... huuh.... huhuhuh.... " Her heavy breaths started to have the undertone of a horses whicker.

Telah's eyes snapped open and she gasped in surprise at the feeling of cold glass on her cock! She looked at it and seen it was growing even bigger! It touched the window from her position sitting on the side of the bed! She needed Marcus NOW. There was no hard cap on how fast the mana can be drawn into her body, so if she doesn't reset its speed she would likely have already completely turned. The sound she heard downstairs was Marcus unlocking the basement door to get food since it was dinner time, that meant there was no locked door protecting him from his wife now though. She came down the stairs so fast and so loud thanks to her hooves that Marcus thought she fell down the stairs at first. He opened the fridge door when he seen her giant constantly drooling cock almost as if to use the door as a shield. She needed to empty out though- not just to give in to her libido, but to slow down the spell! He reluctantly agreed, knowing they didn't have many options and went to go back upstairs to the bedroom, but never made it. Seeing his tail swishing over his equine anus Telah could not resist, and walked faster up the stairs practically falling into him, knocking him to all fours on the steps and then immediately plowed into him on the steps.

As awkward as the pose was, he had to rest is long neck on the stairs to look under himself, reaching around and grabbed her balls and squeezed them together over and over, pumping her balls. They were both giant mutated prostates so it felt good to squeeze them rather than hurt- and they could both be easily touched, if he can force them both to orgasm at the same time he can completely empty her out. Her body went weak from the feeling and she almost fell on top of him. Even in as deep as she could go, half her dick was still outside of his body- it just could not fit. In this position she noticed finally that she was considerably bigger than before overall; Marcus was smaller than her. In the time it took her to orgasm her neck grew another vertebrae long and her rib cage grew another two sets of ribs. When she came into him her even bigger dick caused his guts to cramp, the flare stretched into the sides of his colon locking them in place, but that also prevented any of her insane volume of fluids from getting out of him. She actually backed him back up into his stomach, causing his lower gut to bulge and cramp like he had eaten a meal twice as big as his stomach should fit. It actually hurt to bend his torso because he was so full. They had to wait a bit over two minutes for her to pull back out because her flare locked them in place.

Like last time, changes exploded into Marcus' body at the same speed as her spunk. His muscles throbbed much larger and fur started to grow and spread from his hooves on all four limbs up toward his torso, but stopped just short of touching his body. His nostrils enlarged and his ears changed just like Telah's- but his ears were almost twice the size! The fur that had grown in was also a bit woolier toward the bottom where it first started to grow. He wasn't turning into a horse- he was turning into a hinny, which means he is only half horse, half donkey. Hinny is similar to a mule, only with the mother having been the donkey rather than the father, which causes them to be ever so slightly different in build and temperament. Telah had layered several equine transformations on to get to the super stallion- but in rubbing off some of that onto Marcus, he has several layers of the spell missing causing him to just get the hinny aspect and nothing else. Telah sighed, flopping over exhausted again and slid back down the stairs slowly on her side. Marcus went to the bathroom to empty his guts and then came back to deliver food from the fridge to her, since she was too tired to get up. She needed to eat a lot- she was burning through most of her bodies resources since the multiplication part of the spell was not yet active causing her orgasms to be generated only from her own bodily materials. As they both ate dinner awkwardly on the stairs she shyly told Marcus they were going to have to be quicker on the draw when she starts to change again. She was farther along than he was, but Telah is the only one with magical mastery. If she completely transformed but Marcus was still fine it wouldn't really help them, because he knows exactly nothing about magic.

Ren came into the house late at night, outwardly looking a bit woozy from studying hard all day without rest. The others rushed to the front door where the kitchen and living room met to see her and ask how things went, and Ren held up a quartz crystal with a grin.

"I did it! I was going to test it on Telah but then I realized it could doom us just as easily as save us. If I messed it up and it did not work in one go, the mana used to cast it would get eaten by her own spell and basically burst-finish what it started. It was also super risky, but I tested it on myself already, and I am still completely human, which means it must work."

Telah was expecting her to activate it but Ren just stood there like a deer in headlights, gawking at the huge dick. Telah's beast was still sleeping from the last time it was pumped into submission, but it was not completely in the sheath either, the head and a bit of the shaft stuck out the end, and the sheath was swelled up fat.

"Uh... Ren?"

"Huh? Oh, yea, right. Sorry I was just... admiring... did it get bigger? It was already... so... hah... so good..." Her voice became breathy as her heart started to beat harder.

Both Telah and Marcus took a step back as Ren suddenly lurched forward, her eyes widening enough for them to plainly see her pupils stretch into rectangles. Her iris widened till the whites of her eyes could not be seen anymore and an orchestra of popping joints could be heard as her body jostled abruptly with all the rapid shifts! Her ankles hiked up so fast she fell onto her hands but instinctively landed on her fingertips pursed together. Rather than buckle from the force of the impact they pressed into one another and fused almost instantly. She stomped her hands and feet on the ground like a person impatiently waiting to go to the bathroom and with every strike against the floor her nails grew larger till she was on hooves.

"S-so.... HAAAAwt. YEEE-or cock soooo good..." Ren took awkward steps toward Telah who stepped back at equal pace, though her cock started to flop more into the open.

Ren winced and scrunched up her face, turning her head a bit from the itchy sensation as her hair line advanced down into a mane at the same time her ears stretched up taller and taller, becoming double the length of even Marcus'! She lurched forward several times opening her mouth but not making a sound. They could tell by the firmness of her brows she did not know what she was doing either, which was why she tried to resist it, but was losing the fight.

"H-h.. eeeeeeee." She wheezed with a bit of a whistle in her throat. "H-HEEE..... eeee.... eeEYAWW!" She blurt out an asinine bray at full volume.

The force of the loud voice moving through her throat caused its changes to spike, yanking her neck longer and longer like Marcus'. Her front teeth became larger along with her nostrils like Telah but hers did not stop there- becoming so huge she could not completely close her mouth around her giant bucked front teeth. They grew so large they yanked her jaws forward, forcing her face to stretch farther and farther out. The shadow of fur started to spread out from the base of her mane and up from around her hooves and quickly overtook her body. Ren bowed her front legs and her elevated ass exploded in size, becoming gigantically round in one burst of growth so only the bottom half of each ass cheek actually fit in her pants, and then with a second burst of growth that also swelled her leg muscles tore her pants off completely, falling down around her hooves. Her anus and labia both inflated large and pillowy, matte black. The black skin color advanced up her body as well, but since she already had a layer of fur you could not actually see. Her pectoral muscles swelled huge and her front legs bulked up as she straightened them again. Her pectoral muscles quickly stretched and swallowed up the mass of her breasts, but at the same time the flesh in her crotch swelled up. Two short but fat black nipples popped out as two soft mounds built up under them, inflating into equine teats. Normally when not being used to make milk, equine teats fold in on themselves somewhat to the point of being almost unnoticeable, but hers remained the same size her human breasts were, making them look engorged with milk even though they were empty. Ren's rib cage extended making her torso barrel shaped. Her limbs locked into a quadruped stance, pushing her pectorals up forward more. As her changes finished her now ping-pong ball sized clit popped out, parting the black curtains of her equine pussy and her inner walls clenched so hard she squirt a short stream of lube out onto the floor a half foot behind her!

Telah quickly got behind the kitchen counter and circled it opposite of Ren who was clearly trying to get to her, never breaking eye contact with the giant cock in a lazy arch from Telah's sheath. Her dick was fully out, but too spent to actually become erect. All the more reason to evade Ren.

Marcus tried not to look at his sister's now asinine pussy in plain view, unintentionally pointing it at her brother to face Telah. "What the hell happened? Why did it suddenly just backfire now?"

Telah shook her head. "I am pretty experienced with magic and even I have no idea what the hell she did to get these results."

"What do we do?"

"I know you're not going to like this answer but... you need to get her off."

Marcus' face went beat red. "She's my sister!"

"If I do it, it will speed up my changes, which will then speed up your changes and things are already progressing too fast! I am finally spent for now, if I antagonize the changes even now..." Ren tried to make a run for her, but Telah shoved the counter to the side to pin her temporarily. "And she is not going to give up the hunt. She is in full blown heat."

Not seeing any alternative other than all three of them living as animals, Marcus was forced to agree. Telah quickly ran upstairs to get as far away from the horny Ren as possible and put the image of her wet, winking pussy out of her head. Now that Telah was gone, Ren let out a whining bray before looking to her brother, and locking eyes with his equine sheath. He had no intention of mounting her though. She made some strange staggered braying sounds like she was trying to speak english even though she couldn't. She turned and bumped her massive haunches against him, trying to entice his dick to come and play. He grabbed her butt and turned her the rest of the way around and averted his eyes to over her back as he placed a hand on her searing hot black mound and slid his fingers in. As soon as she felt the pleasure of his touch she thrust back on his hand and her pussy ate the entire thing! He pushed into her a bit more and his arm sunk past the wrist, then she thrust again pinning him against the wall, and slamming his arm in almost to the shoulder! Marcus was more muscular, but still normal human sized, so nearly his entire arm fit. She let out breathy half-brays like wheezing breaths as she thrust back on him and he shoved his arm into her. When he pulled his arm back out to push back in, his elbow rubbed right against her large clit. In her heat she was especially sensitive and it only took a few minutes for her to bray loudly in triumph and cum explosively, soaking her brother's entire right side with her juices. Ren bowed forward a bit, then leaned dangerously far forward suddenly as her pupils abruptly collapsed back into circles. Her iris tightened back so you could once again see the whites of her eyes and the confused look in them a moment before her entire body exploded into colored mist, and a naked, perfectly human Ren fell out from where the donkey was! He heard Telah shout 'get her out' from upstairs in a bit of a panic so Marcus grabbed his jacket off the hook by the front door and tossed it around his sister, telling her to go to the barn for now. Ren still did not know what was going on- she did not fully recall her transformation, it was a blur to her.

Marcus went upstairs to check on Telah, who was looking nervous. "Figure out what happened?"

"Not exactly, but I have some ideas. I think she used a type of purification spell. It wards off any attempt to tamper with things magically or alchemically, which could be mistakingly used to revert changes like mine."

"But...?"

"But she probably layered it with reversal spells to mine, but they are completely different types of spells so they don't really work together. It would not work on me, because I am already half changed- the purification spell would not know what half of me to root for, and since I layered several transformations, it is more likely to side with them than with my human self- since there is only one of those."

"Why the hell would that turn her into an ass though?"

"My mana flow poisoned hers. It seen the powerful flow of equine traits and her seeing my... endowments sparked an animalistic side of her, which then tipped the scales and caused the purification spell to turn her into a donkey, thinking the human Ren was the invader. She turned back to normal once you got her off because without her horniness to tip the favor of her spell, it realized again she is supposed to be human. Once it switched which form it favored, it reverted her. That means if she gets horny again, she will probably transform again."

"Great. So my sister has a thing for horse dick..."

"W-well no, that is probably part of my spell. She likely was unable to find the reversal for that, or just overlooked it."

"So she has parts of your spell on top of a haywire spell of her own. Wow... not looking good for us now. Wait, how did you know she reverted?"

"That is why I told you to get her out of here- I could feel the shift in mana. Her transformation abruptly killed the flow of mana in the house, but then it exploded back out- signalling that she had turned back."

"Wait so why don't you use her to dump your mana into? Her transformed state is already totally equine, but can also revert fully human, so if you fire off your mana into her when she is already transformed..."

"It won't be absorbed. You're right- she will be immune to it, but that is also why it won't work as a mana dump. Her body won't absorb any of it. Just like if you finished your transformation into a hinny I will no longer be able to use you to slow my transformation, and we will be out of time."

"Wait! Her spells draws mana in almost instantly, unlike yours. What if we deliberately put her with you, then she transforms and acts like a mana sponge, then I bring her to the opposite end of the ranch and get her off, exploding mana far away from here."

"I mean, the mana would still be fairly close, but yea, that would work. We need to spread everything out as far as we can to buy us as much time as we can. Tell Ren the plan, and get her working on that reversal spell again... I know she is probably tired as hell but all three of us are doomed if she can't make it..."

Marcus told his sister their plan- avoiding telling her how they manage to revert her transformation out of embarrassment. She had a pretty good idea anyway- she still had the memory of what happened it was just a jumbled mess in her head. Ren tried her best to work into the night but all the strangeness and the already long day of nothing but trying to piece together custom spells exhausted her, and she fell asleep on the desk. Marcus slept on an old couch in the basement, and did not bother to lock the door- if Telah starts changing she needs to dump quick to kill its momentum. Her entire lower half was basically already horse, plus many changes in her upper half now as well. She was probably more horse than human at this point.

Having seen Ren transform almost instantly into a insanely horny ass did not help Telah keep her thoughts straight. Now she was attracted to her own body and extremely impressive dong, but her husband had an impressive set as well- and the fact she was changing him was a bit arousing too. Worrying, but also arousing. She had gotten pretty good at fighting her thoughts when she was awake- she still had no defense against her dreams. It was like her previous horse dream, except Ren was a donkey standing on its rear legs. She was braying but in the dream Telah somehow still understood her fully, but where the conversation ended, Ren spun around, slammed her front hooves down on the desk bending over so her ass slammed into Telah's crotch in a not too subtle hint. Telah immediately started thrusting into her as the mare from the first dream ran by. Telah moved to try to catch the mare, even though her dick was in Ren so that obviously couldn't happen, forcing them both to slide further down onto the floor and as soon as they did, a fully hinny Marcus slammed down on Telah's back abruptly and started pounding her from behind while she pounded Ren. Back in the real world she was gently thrusting into the air, the sheet over it sliding down the erect cock from its movement. Every second thrust it grew a tiny bit larger. The bridge of her nose continued to expand, putting it level with her forehead practically and then her entire face started to stretch, putting a gap between her front and back teeth. She was snorting softly like a rutting horse. The dappled grey skin started to spread up from her crotch covering more and more of her body, while the original spots continued to darken to black to match her genitals. Her balls were black as well as the base of her cock- it quickly transitioned to pink just after the medial ring, looking sort of like it was dipped in pink paint. Her pectoral muscles increased in size and her rib cage popped softly as it expanded larger, robbing her arms of a bit more mobility. Her lungs expanded in size greatly to match her large nose; allowing her to take massive breaths. Her breasts were stretched almost completely flat and her areola started to fade away into normal skin, though her nipples still hung on for now.

By the time Marcus woke up and went to go check on Ren, Telah was waiting on the bottom of the stairs, a trail of precum dribbled up the stairs leading back to their bed, since she was dripping perpetually. Marcus hustled to get Ren, finding her still sleeping on the book, naked except for his jacket thanks to the chaos of the night before. They did not even have time to discuss how much she got done the night before and sent her into the house right away. Marcus then headed into the back of the barn to find some reins. They had not been used in ages so they were packed away but they still had at least a couple. He would need them to yank Ren away from Telah once she was fully transformed and basically acting like a mana grenade.

Ren's thoughts faded out the moment she walked into the room and got a whiff of the masculine musk thanks to Telah not bothering to shower yesterday. Her human thoughts remained only long enough for her face to turn pink in embarrassment as her eyes locked with the huge dick... now even bigger. Thanks to the growth in her sleep, her dick would now be at the top of her head, if it was able to stand up, but in a standing position it was now far too heavy to point straight up without help. Telah was frozen in place, her mind blank trying to fight off arousal as her cock continued to pump salty hot liquid all over the floor. Ren started to walk toward her, transforming rapidly, first her eyes as her mind faded and then she fell onto all fours and resumed her advance. Telah felt her mind clear a little bit. She was still tremendously horny and backed up feeling, but her transformation halted- Ren stole all the mana. Ren let out many lewd, loud moans and girlish groans that quickly distorted and deepened into animalistic brays as her face and neck stretched back out. The zipper tab exploded off the jacket as her torso grew, but she remained wearing the stretched jacket- it did not rip thanks to the zipper popping open. She arched her back as her butt became a huge donkey rump and her changes finished. But their plan had a fatal flaw- Marcus was too rushed to have prepared, he was still finding the reins and Ren was already transformed. Ren rushed Telah who barely had time to get up into a full standing position off the stairs. Her colossal dick made it very hard to move around and she was trying to stand with hooves so her balance was already not great. Ren practically tackled her, climbing over her to pin her to the stairs. She licked up the shaft as she walked further forward till her tits jiggled over Telah's face, then she thrust back so the head of the giant cock wedged between her huge ass cheeks. Ren wiggled her tush till the head wedged its way over her hungry cunt and then stepped down a stair, braying loudly in satisfaction. Marcus heard the bray and frantically started to search in a panic, realizing Telah must not be able to hold off Ren. Ren took another step down and hilted on the huge cock. Even in an actual donkey the entire dick could not fit- there was still a fifth of it exposed at the base. Telah could not resist the pleasure of the donkey's inner pussy rippling along her mutated dick and thrust in. Every time Telah thrust into Ren, Ren let out a short bray because the cock was so huge it forced a bit of air out of her lungs. Telah involuntarily let out a breathy neigh as she came and Ren braced herself and grunt several times as the flow quickly filled her, and then exploded out from around the shaft and continued to pour out down the stairs like a small stream. Telah had enough of her wits about her to panic when she seen how Ren's legs trembled as the cum blasted out of her. She climaxed from being overflowed... which means their mana bomb was going off directly on top of Telah.

Marcus burst through the front door with the reins hanging around his arm hooves just in time to see donkey Ren explode into vapor again and the normal Ren tumble down a few steps, getting covered in clear cum along the way and looking terribly confused. Telah was breathing rapidly, now her mind was blanking on its own without her trying as her pupils started to stretch sideways and her iris widened, though not all the way. Her face continued to crack and snap as it extended almost entirely into a proper horse head.

"I... can't f-feeieieight... this- heieiei!" Her neck started to grow longer as well as her ribs. "M-marcus.. neieieid..." Her voice had become so deep.

She managed to roll forward onto all fours and climb down toward Marcus. Her flare did not even shrink back down fully, and the size was immense... there was no way she could fit that into him! She still got him to try. Marcus got down onto all fours and Ren scrambled to get to the spellbook, seeing they were dangerously low on time. Telah lined up with his anus and thrust several times but it was not going to go in. Telah's balls audibly made gurgling sounds like air bubbles in a watercooler as they started to grow larger! Her precum was gushing out of her now like a broken faucet, and since her cock was wedged against Marcus, the mana shimmered through the fluid into him. His hips cracked loudly causing his back legs to buckle from the abrupt shift and unintentionally slammed his anus down on the cock and popped the head in! His hips were growing larger, his haunches expanded massively and his butt grew huge as his own lower half became completely animal! Telah was able to fit more and more into him as the tried to frantically scramble up his torso further with her front legs. Her nipples vanished from her chest entirely and her pectorals shifted forward more as her chest expanded even further, both in width and length. Precum was now flowing from her so readily it almost seemed like she was already cumming. She managed to slide Marcus down to her medial ring. Marcus' face started to stretch farther out and the fur advanced up his lower body. Slowly her dick started to slide out of him on its own, without actually withdrawing. It was growing still bigger, forcing Telah to step back again and again as less and less of the behemoth could fit inside of him. His gut bulged obscenely and he could feel her dick being rejected by his body- it absolutely could not fit. It was getting so thick even the very tip could not fit inside of him, even though his ass and guts were fully beast. Even standing on all fours, Telah's giant mutant balls were brushin the floor, still making gurgling and sloshing sounds as they bounced and swung at the same time. Even her taint had swollen up like a balloon from the constant pressurized flow. Finally Marcus popped off abruptly causing him to stagger forward and groan as his gaped butt tried to shrink back down to a normal size.

He was barely human, and so was Telah. She was like a stallion with vaguely human features. Marcus apologized to her, knowing he could not help her anymore and ran to get Ren. They had no choice- they would have to finish the counter spell without Telah to advise on it. Marcus tried to get up on two hooves but could not remain balanced for long, and not nearly enough to walk, forcing him to walk on all fours. His own dick was flopping out in the open with a half chub from being plowed by Telah but neither being able to finish. Marcus called over to Ren but she did not respond, likely too absorbed in reading. It was not till he got closer that he seen her foot tall ears and tasseled tail whipping around. She was breathing heavily and staring at the book with wide, wild eyes. Her top row of teeth were getting huge and her nostrils already growing.

"M-marc... look at HEEE- all the hoAAWt drAWWings! Hee... heeaaw! HaaAAWny!" The diagrams of the equine in the spell book and size charts for proportional morphism were turning her on!

They failed to remember that Telah's spell was slow acting because it was intended for other targets. If Ren's horniness was a result of a part of that spell that was not corrected, then her initial levels of libido were not the full scope of its strength. And since her own ill advised spell changed her into an ass whenever her mind rolled animalistic gutterballs... Ren would have an increasingly hard time remaining human. Till eventually she cannot revert at all, and remains a donkey and in full blown, unending heat. She groaned and squirmed in place, putting more of her weight on the table as her body quickly shifted back into a donkey against her will. As soon as her eyes changed and she looked hungrily at the lazy hanging cock between his legs, Marcus knew to run. He ran back to the house and turned to lock the door but stumbled against it and then slipped on all the fluid building up on the floor! He was too much animal to lock the door! He looked at Telah who now looked completely horse, except for her eyes which only now changed the rest of the way, the iris darkening as they expanded to hide the whites of her eyes and her wide pupils stretching out into full rectangles. Ren burst through the door, knocking Marcus down unintentionally for a moment, splashing on the floor. The entire ground floor of the building was covered in an almost inch deep layer of clear cum! Telah neighed and whickered frantically from the feelings. The pulsing tightness inside, the extreme pressure from the impossible volume of fluids and her still growing endowments sent her over the edge into orgasm without doing anything else. Her cock still grew, stretching longer and longer, the flow from its end was like someone crashed their car into a fire hydrant. The flow hit the table and chairs in the kitchen with enough force to shuffle them across the floor. It blasted out in pulses, occasionally slowing down for an extra long pause as what fragments of human mind Telah still had tried to force it to stop, but could not. There was too much in her, and the flow felt so good that her orgasm triggered more orgasms. The gap between pulses started to shorten more and more, moving to make this her last orgasm- one that never ended, ever. Her balls grew to such gigantic sizes that Telah had to balance her weight on her front legs, her rear legs lifted off the ground by the churning black balls under her. She folded her rear legs into a sit and bowed her head, eyes closed as she panted and grunt heavily, climaxing harder and harder from her absurdly hypertrophic penis. It was so thick it took up the space between her front legs and practically doubled the length of her body.

Ren was quick to pin Marcus like she did Telah before, preventing him from getting back up. He tried to push her off but his body was so fully animal already he could not really move his limbs sideways at all to shove her away, he could only nudge her back to almost no effect. Her mind was too far lost in heat driven madness to process the fact her prey was a sibling. She stepped forward lightly slapping him in the face with her equine tits and then sat back onto his dick. Once inside her warm love tunnel it returned to full erection. Marcus' vision started to alter, becoming a bit blurry when he tried to look up and down. His pupils were stretching to better track horizontal movement. He could feel his neck bulking up a bit more and the fur consuming the few sparse patches left on him. The constant flow of cum was overflowing excess mana off Telah and into him, finishing his transformation fully into a hinny, fucking his donkey sister with his back submerged in an inch deep pool of hyper horse cum!

A few days later a Magister at the local library got quite the surprise when he left work to find a hinny scratching the message into the ground outside the building; 'I need paper and put a pencil in my mouth'. Marcus never got the hormone craze part of the transformation, leaving him with enough of his regular mind to just walk into town and get help from someone who actually knows what they are doing. And this is why somewhere in every contract at RHE is the phrase 'Do not try this at home'.