Twilight perused the tomes on her shelf with a sluggish gait. Her fingers glided over the titles, internally tutting whenever the title failed to relate the topic to her mind. The moon had long been hanging in the sky for a while now, yet sleep avoided her or rather, she avoided it. It lingered in her head overly long, the issue that plagued her for most of the day. Each of her friends - barring Fluttershy and the nowhere to be found Rainbow - shared some unusual things in common this day: all were found face down, all had semen leaking from different abused holes, all in a lust drunken stupor that rendered their expression smiling with glee. What’s more, none of them could remember why. After time had passed they were all more angry than sad when they realised what had happened to them, the apparent ecstasy overshadowed all their negative feelings about the enigmatic incident and admittedly, Twilight felt a teensy bit envious that they all had such an experience except her. Regardless, she set about researching what had happened. None of them could remember the assailant, and she had spent so long toiling over the incident that by this point she arrived at the theory it was some kind of invisible sex ghost…

I’m so tired, she lamented internally, rubbing her eyes with her thumb and forefinger. She needed to find out what had happened, and she needed to find out now.

Crash!

“What!” she exclaimed in surprise, her wings instinctively unfurling as she looked toward the crack in her door with widened eyes. She was now alert and tiptoed toward the door. Admittedly, this was partly a facade. She was, after all, a near omnipotent alicorn with tremendous power. In theory, she could easily cast aside any threat that stumbled in through the door… but she did keep some old habits, such as being scared of loud and unknown noises.

She crept through her own castle, barefoot and shrewd, making her way to the colossal front doors. After a minute - so short a time because the library was conveniently close to the door so she could maintain some semblance of her former duty prior to her ascension - she arrived at the corridor, where at the end, or more accurately it’s beginning, resided the door. She was initially alarmed that it was wide open, her horn alighting with cautionary magic, yet when she glanced down, it dispirited.

“Rainbow?” she uttered. She was face down, the quick recognition due to the moonlight illuminating the mare’s messy rainbow coloured locks, and Twilight’s pause instead of going to immediately help her face planted friend was due to one thing: a lack of pants. Rainbow’s taut rear was - unlike her face - directed up. Is she drunk? Twilight mused as she trailed over to the mare, who looked as though she crashed through the doors.

“Wait!”

“Ah!” Twilight yelped, her feet remaining firmly planted to the floor.

“Don’t come any closer,” Rainbow commanded, hand held up, face deadly serious.

“What, why?” she asked, heeding her friend’s words. Rainbow climbed to her feet, and Twilight had to hold back a laugh. “An apron?”

“Yeah, I had to borrow it,” Rainbow spoke with a grimace, crossing her arms. “But that’s beside the point. I have a, uh… problem.”

“Problem?” Twilight probed, looking at Rainbow askew. “What kind of problem?”

“Uh…” Rainbow didn’t know where to start. “A big one.”

“So after we were afflicted with poison joke, you had something of an… alternate, reaction?” Twilight spoke slowly, deliberately, keeping her legs tight together. “And this, ‘extra body’ part you got, was a…”

“A penis, yes,” Rainbow finished, her neutral expression combined with what she was saying was surreal to Twilight.

“And you say all throughout today, unlike other days, you haven’t been able to… control yourself? But so couldn’t, Applejack, Pinkie, Rarity…”

“And, Fluttershy,” Rainbow added, pursing her lips, looking guilt ridden.

“Not, Fluttershy...” Twilight muttered with a frown, looking at Rainbow with her head at a tilt. “So, what, you say when they look at… it, they can’t control themselves?”

“Not just that, but… there’s a smell…” Rainbow said rather descriptively, and Twilight arched a brow. Now that she said it…

“A smell?”

“Yeah. Sometimes when I’m alone, and I get, well… you know, I just can’t help myself but… touch it,” Rainbow emphasized by pointing toward her groin, Twilight resisted looking overly long at the discernible bulge outlining the member through the apron.

“Like a pheromone?”

“Phero-what?”

“You know? A chemical released by an insect or mammal to influence a mate or worker. Like an Ant queen, or a ho-”

“Horse?!” Rainbow finished in exclamation, going wide-eyed. “Twilight, I think that’s it!”

“Uh… how?” Twilight probed, brow raised.

“I mean, I’m not exactly an expert on animals, but I think my ‘little Dashie’ belongs to a horse.”

“Rainbow, I know you're not exactly attracted to the opposite sex, but every high schooler knows that we share a lineage with the common equine. Hence, why they’re of the same particular, erm… shape?” Twilight cringed, half-smiling.

“Nuh-uh,” Rainbow shook her head. “It’s the same size and everything. I’ve seen a dude’s cock before, Twilight. They aren’t even close,” Rainbow couldn’t help the trickle of pride that came through in her words, but she had to avoid thinking about it for too long lest she becomes hard. She needed to solve the problem, not exacerbate it.

“Wait, so right now, you’re not…”

“Hard?”

“Yes.”

“No.”

“Oh…” Twilight glanced back down. It’s a big bulge she observed, suddenly feeling a tad hotter beneath her collar. If it truly was releasing pheromones, then that’d mean Rainbow was in some kind of rut, and it was triggering some primal part of their DNA that was triggering some kind of hyper-estrus. “So why did you come here?”

Rainbow sighed, steeling herself. “I need you get rid of it. I can barely control myself anymore, and everypony who I stay too long around can’t either,” saying it was almost akin to a druggie realising they had a problem, a burden lifting from her shoulders.

Twilight heard her, but along with hearing the request for help, something spiked within her, something that wasn’t new to her; actually, it was a common occurrence with a mind such as hers: curiosity. Now whether this curiosity was driven by a genuine scientific mind or an almost foreign lust in her soul she didn’t know.

“Well, Rainbow, before I can remove it I need to see it, don’t I?” Twilight was unsure if this was a lie or not.

“Uh, okay,” Rainbow replied, unsure. “But you have to remain calm, capiche? Or else…”

“I’ll be completely professional, Rainbow. I promise,” Twilight assured, placing her open palm up in a vow. “I am, first and foremost - even above princess and friend - a scientist.”

Rainbow exhaled. “Alright. Here it goes…”

She meant to put on something of a ‘show’, but she untied the apron with a nervous slowness and averted her eyes in an almost out of character bashfulness. She could feel Twilight’s eyes on her, but she couldn’t tell if they were ravenous or purely platonic, and whilst she sincerely hoped they were the latter she couldn’t deny a small part of her desired the former. She beat down the lustful thoughts with a mental stick, then she allowed the apron to fall.

Twilight remained stoic. Somehow Rainbow had lost her pants, and she recalled seeing the abandoned apparel at Rarity’s although she couldn’t recall who they belonged to. Her small bosom was clearly outlined in through her soaking wet shirt. It hadn’t rained today, and Twilight could only assume due to her ‘strenuous’ day it was likely sweat. Her eyes trailed down the trimmed athletic frame of the cerulean girl and curtly inhaled when her eyes landed on the offending member. She kept that hidden for a year? Twilight was in disbelief, both at the length of time she kept it secret, and sheer size of the flaccid length. It hung down to just shy of her knees, the soft slab of meat looking like a mutinous broad headed third arm coming from the athlete’s hip. The balls were fat and baseball sized; Twilight could only imagine the volume of semen they produced and very quickly she had to mentally slap herself for contemplating such things. Even now the tidal wave of the mind-clouding pheromone was strong in the air and Twilight tried her best to remain calm and in control, digging her nails into her palm; threatening to pierce the skin.

“O-okay, l-let’s get a closer look,” Twilight stuttered, her arm quivering as she tried to maintain composure.

“Are you sure that’s a good idea?” Rainbow cautioned, her heartbeat quickening at the sight of the crumbling librarian. She knew she had to leave. Now. Or else this encounter would descend yet again into debauchery… but lust kept her legs still, and her lack of inhibition began to make her take in her friend’s form.

Twilight’s body, for lack of a better term, was godly. She recalled prior to the ascension that Twilight was on the pudgy side. Not due to diet, but from being cooped up all day in that library of hers, despite requests from Rainbow. She cute, that wasn’t up for debate. However, upon becoming an alicorn, her body truly matched the new form. Wide hips, legs that went on forever, thighs that looked like they could crush a watermelon, a body that was wonderfully toned not to accentuate strength but to showcase the perfect form that only an alicorn can possess. Impressive wingspan, long spiralled pointed horn, a body that everyone was envious of; the more Rainbow looked at the incorruptible and perfect alicorn, the avatar of perfection for all ponykind... the more she wanted to absolutely ruin it.

“Uh, Rainbow…” Twilight probed, breaking Rainbow from her stupor. “You’re… uh… “

“Wha- oh…” Rainbow looked down, her length began to throb and twitch as it came to life, pumping with blood. “I gotta go no- hey, what are you doing!”

Rainbow was stopped as she tried to turn away, the shimmering purple aura of Twilight’s horn wrapping around her entire ankles and wrists, preventing her from moving. Rainbow was helpless as Twilight crawled along the floor, her eyes glued to the meat stick of Rainbow’s length. “Fascinating,” she remarked, her face inches away from the bobbing length. Rainbow tried to fight against the restraint, but the magic bonds were unyielding.

Twilight, displaying unparalleled willpower, simply ogled the shaft with a keen interest. She reached up, the librarian’s fingers, adept for turning book pages, were now employed for something else entirely. She prodded the length, recoiling with an excited gasp at the twitching reply, her expression going wild, smiling with plenty of teeth. She grabbed it with no delicacy, feeling the thick meaty cock in her hand, Rainbow’s groan barely heard; she then wrapped both of her hands around the girth, the tips of her fingers barely connecting around the large cock. The scientist in her remained strong, and her fingers travelled up the length of Rainbow’s shaft, pressing the medial ring with her thumb and forefinger with a grin; meanwhile Rainbow struggled against her bonds, pre bubbled from the tip of her horsecock. Twilight liked the way the heavy column of masculinity it felt in her hands, and a part of her, past all the cock hungry haze, she was envious that Rainbow had such a powerful tool attached to her. She was partly that the mere contact of her finger tips against the turgid flesh of the appendage was enough to have the athlete writhing in pleasure, cooing out moans of delight; a sensation Twilight sorely wished to mimic.

Rainbow would have keeled over if she could. A sudden and entirely new sensation washed over her. It was weird, but she couldn’t deny it felt good. She saw Twilight was at least a foot away from her cock, sat on the floor with her legs spread, plunging her middle finger into her depths as she watched her with a lusty grin. Rainbow looked down and saw her meat enveloped in a purple aura, Twilight's magic working like purple cock slave on her member. It swirled around the erection as if it were a sentient cast. Every time pre leaked from the tip it simply fell to the floor, little drip drops to join the moaning and wet smacks of Twilight’s fervent masturbation.

Just as Rainbow was about to release her bliss all over the floor, and probably get some on Twilight as well, the pleasure subsided from her; her throat releasing a whimper. Twilight smirked. Rainbow, despite how far gone she was, noticed that Twilight’s horn was still covered in her magic. Rainbow went wide eyed as her eyes snaked down the alicorn’s body, the purple coated women’s hand circled around her own clit, which began to change right before Rainbow’s very eyes. It elongated and widened, rapidly becoming a shape that Rainbow was all too familiar with. Twilight groaned, her other arm propping herself up as she instinctively raised her hips in an involuntary thrust, her newly formed cock growing longer and thicker. Rainbow already in awe at the purple throbbing fuckstick that Twilight now had attached to her. It looked near identical to her own barring the fat ballsack the athlete had, instead below the girthsome rod was Twilight’s moist cunt.

“This already feels exquisite,” Twilight cooed, the erect cock twitching out a bead of pre, independent of Twilight’s touch. The alicorn dragged her forefinger from tip to base, the pleasure coursed throughout her body like electricity, spreading out from the newly formed organ all the way to the tip of her horn; releasing little purple sparks from the tip of the ivory spiral. “No wonder you kept it a secret. But didn’t your parents tell you it’s rude to not share your toys… ”

“Twilight,” Rainbow gasped, regaining a modicum of her faculties, “if you don’t stop now…”

“Why would I?” Twilight giggled, standing up, her cock swaying. “This is the most fun I’ve had in ages, and we’ve only just begun!”

Rainbow didn’t know if she was scared or excited at the prospect Twilight had something of a dominating streak in her, even if it’s only triggered by being outrageously horny. And admittedly, Rainbow was somewhat curious as to what else Twilight’s magic was capable of…

Twilight closed the gap between them very quickly, her cock was thrown toward Rainbow like a dart, the flattened head of the princess’ cock pressed just to the right of Rainbow’s shaft. Rainbow moaned as Twilight compared the sizes, pressing the two fat rods against each other, staining each other’s pubic area with pre; the smell of the combined musks submerging Rainbow’s mind in a cloud of sex, filling her with a starving appetite for cock.

“A near perfect replica,” Twilight remarked, grinning at Rainbow, her finger tracing circles on the athlete’s chest. “You know, I could do a lot more to make this extra fun for us both.”

Rainbow didn’t have time to inquire, as Twilight's horn already was alight and then a feeling of static encompassed her chest; a pleasurable sensation was felt on her breasts through her shirt. The magical binds prevented Rainbow from moving, but they also prevented her from getting the pleasure she truly desired. Twilight’s magic was doing something to her but she didn’t know what, not yet, but soon she began to feel it.

Her chest began to enlarge, she watched it happen with her own eyes. Rainbow’s bosom expanded out, stretching the fibres of her shirt, every inch out they ballooned wracked her body with moans; pre coming from her cock in a steady trickle, drowning in the bliss of it, the sensation keeping her on the edge of orgasm and allowed her to pass no further. Soon she was panting like a bitch, as if the ballooning was physically exerting. Twilight hands squeezed the growing mounds through the shirt, watching and feeling them grow from a B-cup to a C-cup within moments. Twilight enjoyed feeling the fatty tissue between her fingers as Rainbow’s breasts grew, and she couldn’t wait to hear the sound of tearing the fabric.

Rainbow felt the weight on her chest increase, her breasts approaching the size of the buxom women she saw in the magazines. Her cock head throbbed against Twilight, and she gyrating into the adjacent mare, trying to hit orgasm; yet she remained agonisingly far. Was this Twilight’s doing? She didn’t know. Neither did she know how much bigger her breasts would get…

Rainbow bit her lip in both pleasure and pain as the fabric of her shirt was stretched to it’s limit, her breast’s growth being halted by the tight unyielding shirt, the fat of her expanding bosom pouring out her apparel. Twilight released a triumphant cheer when she saw Rainbow’s shirt rip from the centre out, the heavy pillows gave a singular bounce as the torn shirt pieces fell to her feet. Rainbow’s chest was colossal, breasts larger than her own head at the very least double F-cups she assumed, and Twilight smiled at her triumph. Without warning Twilight shot down, taking in one of the pink caps atop the one of the blue mounds into her mouth, her tongue circled the pink nub; Rainbow moaning at the newfound sensitivity in her breasts, yanking her arms at the bindings, so she could try to stimulate her cock.

As Twilight sucked at the nipple, she found joy in seeing Rainbow writhe around in agonising bliss, and very quickly she herself desired stimulation. She began to sway her hips back and forth, her cock sliding over Rainbow’s, causing her to moan into the athlete’s coat, her cock frotting Rainbow’s own. Every time the two erections brushed over each other they both moaned, staining each other’s coats with pre. Twilight sunk one hand into Rainbow’s other breast, the soft flesh like a cushion, only adding onto Rainbow’s considerable plate of ecstasy; Twilight’s other hand went down low, stimulating her soaking slit, groaning.

As the seconds passed, Twilight was eager to try more. She pulled away from the nipple, a trail of saliva connecting her lips to the pink nub. Without warning, Rainbow saw her horn light up again, but this time she felt the sensation that was previously on her breasts now on her cock, and she let out a throaty groan. Twilight giggled, her palm pressing against the crown of Rainbow’s cerulean dick; raising it up so that it was pressing against her stomach. Rainbow released a genuine scream, not of fear, but of sheer ecstasy. She couldn’t see it passed her newly enlarged bosom, but she certainly felt it. She began to feel light headed, her body suddenly bereft of blood, apart from one particular organ…

Rainbow’s cock grew thicker, longer, pre leaking down it like it like a fountain by now. Twilight watched in abject fascination and lust as she watched the organ grow, every throb and pulsating twitch saw it lengthen a few inches and grow a bit fatter. It was becoming heavy, and Twilight even struggled to keep it pressed against Rainbow’s stomach as it lengthened, soon becoming embedded between Rainbow’s massive breasts; Twilight having designated the athlete’s mouth as the target for her horsecock torpedo.

Rainbow was quick to try and gobble the head of her own cock, uncaring of its increased size. Twilight grinned as she watched as Rainbow attempted to take in the tip, her jaw not stretching nearly far enough to take it in. Rainbow, in her lust addled state, was content just to lick the tip like a lollipop, coaxing every tingle of pleasure she could from the repetitious act. Seeing Rainbow lick at her own blue rod Twilight got jealous, and needed to share it.

She pressed against Rainbow, their tits mashed against each other, and their cocks frotting. Twilight leant down, gyrating her hips against Rainbow’s dick as well as joining the Athlete in fellating it. They shared the pre that beaded from the tip, occasionally stealing licks from the other to lap up the delicious liquid. Occasionally, Rainbow would get poked in the cheek by Twilight’s horn, whenever she overzealously went for a drop that was coaxed from the prick. At some point Twilight wrapped her arms around Rainbow, enabling her to increase her gyrations against Rainbow, stimulating both of their cocks simultaneously; her thoughts of being ‘on top’ during this situation quickly evaporated as she became enamoured with the horse member, it’s taste and scent overpowering her. Increasing its size only increased its potency, it would seem…

So lost in the activity was she that Rainbow Dash didn’t even notice when she began to suckle on something else, although Twilight was quick to notice it, in fact, it rendered her entire body stiff. Rainbow was sucking on the alicorn’s horn, the act was similar to having popping candy in one’s mouth, and the magical sparks in her mouth weren’t entirely unpleasant so she kept at it; sucking and twirling her tongue around the ivory spike. Twilight was speechless, or rather, she became incapable of uttering a single sound. Her body locked in place, barring her cock, which continued to throb against Rainbow’s; the combined sensations of which were almost too much for the purple coated girl to handle.

It didn’t take long for Twilight to convulse and groan, tightening her embrace around Rainbow as she came. The fur between her legs were matted with marecum, whilst her cock throbbed several times, each releasing a rope of cum smacking the underside of Rainbow’s breasts. Twilight’s horn fizzled inside Rainbow’s mouth, the magic holding Rainbow aloft faded, then they both fell to the floor together; Twilight panting as she rode her bliss train, uncaring of practically being crushed by Rainbow’s enlarged mammaries. Rainbow had her hands placed at either side of Twilight, teeth clenched, orgasm a hairline away from being achieved for the athlete. Although, after being trapped by Twilight in her magic bonds, she remained enough of her faculties to desire one particular way of achieving her ecstasy.

“Rainbow,” Twilight cooed, the girl in question raising herself up, Twilight parting her legs. For a moment, Rainbow rested her slab of masculinity on Twilight’s purple pole, the heavy member smothering the smaller length. Through it, Twilight could feel Rainbow’s heartbeat, through every twitch and throb. Rainbow pulled back her hips, dragging the just shy of colossal hardness down Twilight’s body, until the wide head of her member prodded against Twilight’s eager cunt; the hole soaking and clenching, ready to receive Rainbow. “Split me in half,” Twilight growled, pushing against the tip, causing Rainbow to release a husky growl of approval.

She jutted her hips forward, penetrating Twilight’s cunt, already give her a feeling of fullness. And it was just the tip! Rainbow’s hands kneaded into Twilight’s thighs, inching more and more of her hardness into the vice like canal, almost in disbelief at the immense pleasure this brought her. The moist walls, despite such a giant intruder, were squeezing and trying to coax more of Rainbow inside; which the athlete was more than willing to satisfy. She snaked more and more her cock into the tight slit until she met resistance part way in. However, very quick did she realise that only a quarter of her length was inside and that she had already hit the cervix. It was a disappointing that she wouldn’t be able to completely obliterate the hole with the entirety of her enhanced length, but since pleasure was at the forefront of her mind she didn’t care entirely for making the love canal gaping and fit for only her cock. If she could do only one thing during this, it’d be to make sure no other pony could bring her to the heights of pleasure she’d bring to Twilight now.

As she pulled her hips back, both of her hands travelled up her thighs, resting them just inches from Twilight’s marecock. When only the flat head of her cock remained within Twilight’s snatch, she softly grabbed the twitching member, the feeling of another’s penis in her hands was a foreign experience for her; but she did fancy the idea of imitating the act her friends did on her to another. She lowered her head down, her breasts dangled, and she took in the head of Twilight’s horsecock; swirling her tongue and sucking with an inexperienced mouth, smiling at the meat as Twilight moaned.

Twilight groaned but then yelped as Rainbow thrust into her, the combining of sensations catching her off by surprise and the athlete didn’t give her time to get used to it, as Rainbow was quick to withdraw and slam back in; smashing against the former librarian’s cervix, increasing the heights of her pleasure. Rainbow was very quick to innovate, realising her larger breasts could be used for more than just show. She squeezed the giant tits, pulling them apart and wrapping them around Twilight’s pole, moving them up and down in a messy fashion, although by Twilight’s loudened moans she correctly assumed that Twilight didn’t care for the athlete’s lack of experience.

Rainbow pounded into Twilight’s cunt, slobbered and sucked her cock, breast fucking the princess using her own semen as lubricant. All in all, these factors rendered Twilight a drooling groaning mess, her hands by her head; fingers twitching. Rainbow took more of the length into her mouth, quickly acquiring a taste for Twilight’s own cock, whilst her thrusts increased in their pace. As she did all this, closer and closer she came to cumming, her erection swelling within Twilight’s canal; every vein along her long becoming pronounced as the appendage flexed within Twilight’s moist pink tunnel.

As orgasm got closer and closer for Rainbow, she could no longer control her hips. The sporadic thrusts were strong, Twilight’s moans became a mixture of pleasure and pain as she felt her cervix get beaten with Rainbow’s horsecock; finally releasing a shriek of pure unadulterated bliss when she felt Rainbow penetrate into her womb, the massive length spreading her even wider as it swelled, the cock flaring within her as it pumped rope after rope of the athlete’s seed into her womb. It was then that Twilight came, sent over the edge by the sheer volume of the cum filling her. Rainbow’s cheeks bulged out as Twilight unleashed her load into her mouth, moaning before her lips gave out and released the deposit all over Twilight’s cock and her own breasts, panting with a smile as she continued to release her own seed. Twilight’s womb ballooned out before the pressure was too much, forcing Rainbow’s cock out of her and releasing a gush of Rainbow’s cum out onto the floor, the gaping fuck hole trickled cum out of it long after.

For the first time today, Rainbow actually felt satisfied, a dreamy smile on her face as she fell backwards; her wings cushioning her fall. Twilight lay limp on the floor, surely rendered unconscious due to sensory overload, her mouth wide open and drooling as she snored. Rainbow breathed, hungry for air. She found herself too weak to prop herself up, her enlarged breasts keeping her down. In truth, she didn’t care, the afterglow of the sex rendered her worries moot in comparison; content to just lie down and ride the bliss into dreamland. It’d work itself out…

Author's Note

Yee, it's out.
But wait, Jackelope, you incomparably handsome bastard, that's all the mane 6 isn't it?
Ey, you put two and two together, reader!

(Apologies if this was bad quality.)