Curse of the Green Sun

by RadPanic

Rating: mature
Tags: Twilight Sparkle, My Little Pony: Friendship is Magic, Romance, Porn, Fetish, Rainbow Dash, Sex
Length: 7660

Deep under the Castle of the Two Sisters, Rainbow Dash has sex with a tentacle monster and gets inflated. Twilight takes an awfully long time to "rescue" her.

For Rainbow Dash and Twilight Sparkle's latest date, they've decided to explore the Castle of the Two Sisters together. Rainbow hopes to find secret passages, traps, and treasures; Twilight wants to search the libraries for one-of-a-kind books and lost knowledge. Instead, in an abandoned chamber deep below the castle, they find a sanity-shattering horror, not meant for the eyes of mortal ponies!

Oh, and they also find a tentacle monster from another dimension.
—————
Fetish porn, of course, featuring: cum inflation; tentacle sex; spit-roasting; cum inflation; all-the-way-through; belly bulging; cum inflation; extreme insertion; implied cervical penetration; bumping and grinding; and cum inflation. Also, these fetishes might be considered spoilers: rape roleplay; consentacles.

This story was a commission from Anon #3.

2017 Feb 22: Added a slight bit before the clop, to make the subtext a little bit clearer.
2017 Mar 17: Name changed from "Green Sun".

Big shout-out to the folks on the Pony Inflation Thread in /trash/.

Published 2017-02-22 05:20:01 UTC
Last updated 2017-02-22 05:20:01 UTC

Pounded in the Butt by the Huge Implications of Meadowlark's Second Theorem of General Magic

In the very heart of the Everfree Forest—a place utterly teeming with dangerous, unnatural life—the Castle of the Two Sisters remained a void of sorts. The flora had yet to reclaim that land, and few were the animals who dared to tread there. On some level, the forest remembered what had happened in that place a thousand years ago, and feared to disturb the peace any further.

On this day, two ponies arrived to disturb the peace instead.

“This is gonna be so cool!” Rainbow Dash proclaimed, zipping through the open door and hovering in the grand entrance hall.

“I know!” Twilight Sparkle answered, trotting after her. “I’ve been looking forward to this trip all week.”

“Why didn’t one of us think of this sooner? You wanted to do book things for our date, and I wanted to do awesome things—but this way, we can do both!”

Twilight rolled her eyes, but still smiled.

“Alright!” Rainbow turned back towards Twilight. “You have fun poking around that musty old library! I’ll see you as soon as I’ve found some cool treasure… So, about twenty minutes!”

“Wait! Dashie, I’m coming with you. It’s safer this way.”

Rainbow landed. She opened her mouth to reply, but Twilight cut her off: “I know, I said the Princesses would never deliberately hide a really dangerous trap in this castle. But this place is old enough, there’s no telling what could be unstable. So we ought to stick together. Look, I made up a schedule and everything!”

Twilight produced the schedule, and it was Rainbow’s turn to roll her eyes.

Twilight continued, “We’ll do your castle exploration for two hours, at minimum. If we don’t find anything of interest within that initial time frame, we both go to the hidden library. If we do find something of interest—”

“Boring!” Rainbow galloped for the nearest passageway. Twilight set off after her.

The two came to a stop in a narrow hallway. The ceiling was a series of arches, supported by columns set into the walls. Between those columns, sconces were affixed to the wall, but the torches intended for them were long gone.

“You know the drill, Twilight,” Rainbow said. “Check everything. Look for anything that’s out of place. Be careful. Be methodical. And if you’re ever in doubt, ask yourself: what would Daring Do… do?”

Twilight chuckled. “Oh, that won’t be a problem at all. But are you sure you can be methodical?”

“Please!” Rainbow began tapping at stones in the wall. “Methodical’s my middle name!” She reached for the nearest wall sconce.

“Just, don’t get disappointed if it takes a long time for us to—”

The sconce shifted at Rainbow’s touch. The floor dropped from underneath both ponies.

—————

Several stories underground was a castle chamber with no apparent entrance or exit.

One of its walls spun, abruptly spitting a pegasus and an alicorn into the room. They were both a bit dazed and smeared with dirt; the alicorn had ashes all over her face.

Twilight brushed the ashes off. “That was… really something.”

“Yeah…” Rainbow shook her head. “But you know what that means? Whatever’s hiding at the end of that gauntlet, in this room, must be totally epic!”

Both ponies looked around the room—and found it was rather less than epic. Although the chamber was easily as large as the grand entrance hall, it was just flat, gray stones—completely devoid of decorations. The only thing in the chamber besides the two ponies was a set of shelves that covered most of the farthest wall. The shelves were loaded with…

“Books!” Twilight exclaimed.

“Books?” Rainbow asked. “All that for a bunch of books!”

Twilight rushed towards the shelves. “Just like you said, this little library must have been really important! So the Princesses had to hide it away, to keep these precious volumes from falling into the wrong hooves. And now, we get to read them!”

Slowly, almost reverently, she lifted a single book from the nearest shelf and opened it. Her eyes widened. “Wow.”

Rainbow looked over her shoulder. “Huh, that’s pretty big.”

“Yeeeahhh...” Twilight flipped to a new page, and gawked at its contents as well.

“Is everything in here like that?” Rainbow grabbed another book and opened it to a random page. “It is! Oh my goodness, can you believe it, Twi? We found Celestia and Luna’s old porn stash!”

“That’s...” Twilight’s right eye twitched, “...great.”

“What’s gotten into you?” Rainbow squinted and leaned closer. “Honestly, this is kinda tame for porn. We’ve done dirtier stuff together...”

“I know!” Twilight scrunched her eyes. “It’s just a little weird for me to think of Princess Celestia reading... this kind of book.”

“Eh, she’s a pony.” Dash slotted her book back into the bookshelf. “Ponies have needs.”

Twilight opened her eyes. “I know that intellectually. Still, it’s just a bit of a shock to have it thrust in my face like this.”

“Hehe, thrust.”

Twilight rolled her eyes. “I’m just saying, it’s a lot to take in.”

“Oh, yeah?” Rainbow spun back towards Twilight. “You know what’s really ‘a lot to take in’?” She smacked the illustration in the book Twilight was still holding open. “This stallion’s package! Am I right?”

“Oh, knock it off,” Twilight said. But she wore a playful smirk as she said it—and as she swatted Rainbow’s rump, lightly, with that book. “But seriously. Celestia… isn’t really my mom, but she almost could be. So how would you feel if you stumbled onto your mom’s pornography collection?”

Rainbow snorted. “How do you think I learned about bangin’?”

“That... would explain a lot.” Twilight leaned closer. “Like why you were so bad our first time.”

“Hey! I was still better than you!”

And Twilight giggled, which dissipated what little of Rainbow’s competitive temper had been stirred up. “Oh, Dashie, only you could turn sex into a contest. Besides, when we do it right, don’t we both win?”

Rainbow shook her head, while still smiling. “And only you could turn sex into a friendship lesson.”

They kissed, just a quick peck, then Rainbow went back to the bookcase. She placed her hoof on the book spine at the left end of the shelf, tipped the book out a few inches, and let it fall back in place. Then she repeated the process with the next book over.

“What are you doing?” Twilight asked.

Rainbow was working her way down the line of books, testing each one in turn. “Checking for the lever that’ll reveal the secret passageway behind this bookcase, of course!”

Twilight opened her mouth, then shut it. Finally, she said, “Well, good luck with that.”

“Come on!” Rainbow placed her hoof on a book that was twice as thick as its neighbors. “Which is more likely: Celestia and Luna went to all this trouble just to hide their rut-books? Ooooor this is merely the decoy to hide something even more valuable?” She tilted the book out. It had a purple cover, a shade so dark it was nearly black.

Twilight said, “It could just scan with my magic to find any—”

When Rainbow released the purple book, it didn’t tilt back into place. It fell off the shelf, landing on its spine with a heavy thud, then opening to the middle. Both ponies stared down at it. The two open pages were an illuminated manuscript, dominated by an illustration in the center. This depicted a green sun shape—its color deeper and richer than any ink Twilight had seen before—with a half-dozen mares and stallions tangled up in the wavy arms of the sun’s rays.

A closer look confirmed all of the ponies were in distinctly obscene positions.

But before either pony could examine any further, a green aura surrounded the book, and the entire volume levitated a foot off the floor.

“Whoa!” Rainbow said, backing away. “Did you do that?”

Twilight followed suit. “No, I think that’s the book itself!”

As they watched, the illustration began rippling, in a way that hurt to look at. It no longer appeared like ink on a page—instead it seemed to be a hole, through which could be seen a writhing mass of green vitality.

“Twilight, should we be worried?”

“Maybe...”

There was a sound that set Twilight’s teeth on edge—the combined tearing of something wet and scraping of something dry—and a thing emerged from the pages of the book. It was the same shade of green from the illustration, and it was long, tapering to a nub. It was like a headless snake or a leafless vine. It twisted and coiled in the air as it extended farther from the book: three feet, six feet, nine feet. Another of those elongated shapes grew out, and then two more. Their skin was smooth and shiny—slicked with otherworldly moisture along their entire length.

“Seriously?” Rainbow rolled her eyes. “We finally get to see an eldritch horror from another dimension, and it’s just a dumb tentacle monster?”

Twilight blinked. “Yeah, looks like it.”

More tentacles emerged, making a total of eight, waving languidly in the air.

“This should be a piece of cake!” Rainbow crouched into a fighting stance. “Alright, I’ll fight it off while you do your egghead thing and banish it, or whatever. Got it?”

“Actually, we should probably—”

“Great!”

Rainbow pumped her legs and beat her wings, and she was off like a rocket. Once, twice, she circled the chamber in the blink of an eye, building up speed. When she dove at the beast, her hooves hit like a ton of bricks. Four of the tentacles recoiled from the impact. The others tried to grab her, but Rainbow was much too fast.

“Wait!” Twilight called out.

Ignoring her, Rainbow dove again. This time she only struck three tentacles. The other appendages were quicker this time when they twisted towards her, but Rainbow still dodged them effortlessly. Again and again, she dive-bombed the monster, ducking and weaving around every attempted counter-attack, even as it sprouted even more tentacles.

On the twelfth attack, one of them finally brushed against Rainbow’s left hind hoof. That knocked her off-course—not from the tiny force of the impact, but from the unearthly chill that rushed over Rainbow’s entire body. She hovered outside the monster’s reach and shook her head.

Twilight called up, “Rainbow—”

“Not now, Twi!”

Yet again, the pegasus rushed into the breach. There were over a dozen tentacles now; Rainbow kicked some and dodged the rest. Once, she dove, then twice. But on the third pass, she felt the chill once again, and a pressure around her rear hoof—a tentacle had grabbed her.

“Hey!” Rainbow shouted. She zoomed away from the monster, intending to shake it off. But the tentacle held tight, tethering her. Rainbow grunted and pumped her wings even harder, but nothing happened—until another slimy appendage grabbed her other hind leg. Rainbow gave a furious snort and spun in the air to attack both tentacles. But in spite of her foreleg strength, she couldn’t build up enough momentum to do any real damage. She might as well have been punching a brick wall. As her forehooves rained blow after blow on the green limbs, they slowly slithered up her hind legs, creeping around her hocks and approaching her haunches.

Rainbow pulled back for yet another punch, but suddenly found two more tentacles binding her forehooves. “Hrrr! Rrrrrgh!” She strained and tried to pull free, but the appendages only tightened around her limbs. Two more darted in and wrapped around her wings; Rainbow Dash was well and truly trapped.

But she wasn’t going to give up without a fight. “Grarrr! Let me go, you stupid…” She twisted and writhed, trying in vain to pull free of the binding tentacles. As she arched her back, the creature slowly lowered her towards the floor. All the while, those slimy limbs slid further and further up her legs and over her body. They curled around Rainbow’s shoulders and haunches, while holding her wiry legs splayed straight out. More tentacles explored her torso, pressing in a firm-yet-soft manner that Rainbow could almost mistake for a massage if she would close her eyes. They slithered over her muscular chest; they squeezed her trim stomach. One even threaded between her haunches, brushing gently as it explored up, towards the base of her tail...

In spite of the tentacles’ coldness, Rainbow suddenly felt warmer. The tentacle wrapped around her dock—and when she redoubled her efforts to squirm free, that just rubbed her loins against that tentacle even more, a sensation she found most distracting, even under these circumstances...

“Yellow.” Twilight spoke with authority; her unraised voice echoed through the suddenly quiet chamber.

The tentacles went completely still, aside from lowering the bound pegasus closer to the floor. Rainbow continued wriggling all the while—but she only succeeded in getting sweatier and more bothered, until at last she found herself face-to-face with Twilight. “Hey, I could kinda use some help here,” Rainbow said, panting and squirming within the tentacles’ grip. “Have you figured out how to banish this thing yet?”

Twilight said nothing, and just raised one eyebrow. With her telekinesis, she held up the book that was causing all this trouble. The transdimensional portal, anchored to the book, moved as well—but somehow Rainbow remained at eye level, suspended by those motionless tentacles. As she squirmed in their grasp, she kept rubbing herself against her bonds, accidentally teasing herself as her nethers repeatedly brushed the tentacle directly behind.

“C’mon, Twilight!” Pant, pant. “What’s taking so long?”

Twilight thrust the open book in Rainbow’s face. The pegasus’s gaze was drawn to a paragraph specifically highlighted by Twilight’s magic. As Rainbow read, her eyes widened, and even more sweat broke out on her forehead.

So, that’s how it’s gonna be? she thought. Okay, then. “Green.” Show me what you got…

The tentacles unfroze and embraced Rainbow all over, briefly squeezing her legs, haunches, and torso even tighter. The one behind released her dock to begin prodding her loins in earnest—and Rainbow’s body betrayed her, bucking into the slimy intruder.

The book lowered; Twilight and Rainbow were once more eye-to-eye. Twilight wore a wicked smile. Rainbow gulped.

The tentacles shoved Rainbow to the floor on her belly—hard enough to knock the breath from her lungs, but not quite hard enough to leave a bruise. After gasping for breath, Rainbow called out, “Twilight! Please, help!”

“Oh, no!” Twilight proclaimed, taking a few steps back. “My brave knight, Rainbow Dash, has been overpowered by the vile Green Sun! And my magic is useless against this filthy, lecherous creature from beyond the stars.”

Rainbow gasped again. The tentacles resumed massaging her all over—more forcefully, more salaciously. They were trying to turn her on, and damn it all, it was working. Three of them pushed down on her withers and the back of her neck, holding Rainbow’s head to the cold floor. Another one wrapped around her dock—and it, with help from two more between her haunches, lifted her rump a few feet into the air. Rainbow whimpered and tried to pull out of their grip—tried to at least squirm into a less compromising position—but that just coaxed a teat massage from the tentacles below, and more insistent prodding at her nethers from the tentacle behind.

Twilight continued, “Our only hope is that these books have some crucial clue about the Green Sun, which I can use to free my beloved.” She flipped a few pages in the book—which somehow didn’t disturb the tentacles emerging from the book at all—and began poring over the text.

“Stay strong, Rainbow Dash! Think wholesome thoughts, and perhaps the Green Sun will leave you undefiled!”

It was too late for that. Without warning, the tentacle behind rammed into Rainbow, penetrating her three inches deep within a second. “Uugh!” she cried, in the brief moment that the tentacle gave her before it thrust again. Then again, and again—farther and farther the boneless limb slid into her canal, a few inches at a time.

“Hmmm…” Twilight muttered. “Transdimensional portals, yes, yes. Intersections between our dimension and the Green Sun’s home dimension? Very interesting…”

Rainbow rocked forward and back with the invader’s motion. “Twilight—” Thrust. “—please—” Thrust. “—hurry!” It was revolting, both figuratively and literally: her body apparently disagreed with her mind on how wrong this ordeal was, and now her haunches were bucking back in time with the tentacle’s thrusts, coaxing more and more of its length inside her. Rainbow still tried in vain to escape, but her own hips’ reflexive thrusting made each wriggle for freedom weaker than the last.

“Hmm…” Twilight said, casually flipping the page. “Fascinating…”

All the while, other tentacles continued massaging Rainbow—on her withers, her teats, at the base of her wings—spurring her treacherous body into even more arousal. “Twi…” Thrust. Thrust. “I…” Thrust. Thrust. “I can’t…” Her eyelids slowly lowered as her mind began drifting away—only to open wide once more.

“No! Not there!” The Green Sun had penetrated all the way down Rainbow’s canal; now it pressed against her last barrier. “No further!” she pleaded, as a sudden surge of adrenaline let her raise her head off the floor. But only for a few seconds—another tentacle shoved her back down, and yet another cushioned the stone beneath her. All the while, the tentacle inside simply waited; it flexed and contracted along its entire length to continue stimulating her, but made no forward progress.

“Yeah,” Rainbow said, “just stay right—Yeeargh!” It thrust again, penetrating into her womb, and then again and again.

Twilight read aloud, “‘See also: Creatures of the Ninth Ring.’ Don’t mind if I do!” She flipped nearly to the end of the book and resumed reading there.

Rainbow’s eyes widened again as she felt the tentacle press against the far wall of her uterus. If this were a stallion, he would have nowhere to go but back out; but the Green Sun was no stallion. The thick, meaty appendage just kept thrusting forward, curling around itself as it steadily filled Rainbow’s womb with its boneless mass. Soon enough, there was no more room inside, but the creature didn’t pause at all—and her womb began to stretch as more and more of the tentacle pushed inside. Even with her head pushed to the floor, Rainbow could see her belly bulge out—one inch, two inches, farther and farther.

“Please—” Thrust. Thrust. “—no more!” Thrust. Thrust. “Twili—!” Another tentacle cut Rainbow off by slapping her cheek. At that, her eyes rolled back, and she moaned incoherently, her tongue lolling out. Her whole body tensed, and she bucked her hips—faster, more erratically than before. All the while, the tentacle continued methodically thrusting into her, filling her larger.

“These higher-dimensional life forms have their own ecosystem!” Twilight said to herself. “And it’s so complex, I could study it for weeks and barely scratch the surface!”

Rainbow’s gut was the size of a watermelon now. It squeezed against her haunches as it swelled larger and larger; it jiggled and swung with every jerk of her hips and every thrust of the Green Sun. Eventually, she slowed and went limp, her only motion that of the tentacle rocking her forward and back. She let out a long sigh. Finally, her eyes refocused, just as her tail was released from that other tentacle’s grasp. It didn’t need to hold her rump up any longer: now her gut was stuffed large enough to raise her whole backside off the floor.

“H-hey…” Thrust. Thrust. “That’s—” Thrust. Thrust. “—that’s ee—” Thrust. Thrust. “—enough now!”

Then Rainbow’s eyes widened once again: where the tentacle emerged from the book-portal, it was swelling up. Once the bulge was slightly larger than a soccer ball, it began sliding up that long, green length. Its progress was slow but steady—drawing closer to Rainbow just slightly faster than that same tentacle was thrusting into her.

“Twilight?” But the only answer Rainbow got was another slap in the face from a tentacle. It just stung slightly, more of an annoyance than a pain, but the intent to demean was clear as day. Meanwhile, her hind legs splayed further out as her gut swelled, inch after inch adding to its diameter. And behind, that bulge crept closer to Rainbow’s backside; about eight feet of tentacle remained.

“Twilight!” Another slap. Thrust. Thrust. “Kinda—” Slap. Thrust. Thrust. “—running—” Slap. Thrust. Thrust. “—outta—” Slap. Thrust. Thrust. “—time—” Slap. Thrust. Thrust. “—here!”

“Oh!” Twilight said. “Safari Hat wrote an entire book on xeno-ecology! I wonder if the Princesses had a copy… Oh, they did!” She set down the purple book with the tentacle portal, and cracked open a new book from the shelf.

The bulge was about six feet away, now. Rainbow called out, “Twiluuumph!” The tentacle in front, no longer content with slapping her, invaded her mouth. It slithered past her tongue, overpowered her gag reflex, and wriggled a few inches down her throat before pausing. Then it thrust forward again, then again, causing her neck to bulge as it pressed forward.

Rainbow tried to cry out around the mouthful of thick, boneless appendage: “Hrrrmmm—” Thrust. Thrust. “—mmrrrnn!” Thrust. Thrust. “Mnnmmm!” The two tentacles were perfectly matched, each thrusting at the same time into her mouth and loins, respectively. Rainbow would later wonder if this was how an accordion felt—being smashed from both ends at once—but at the moment, she had other concerns. After all, the thick rods of meat impaling her from both ends were pretty hard to ignore, especially since her treacherous body was enjoying even this latest degradation. And there was still that bulge in the tentacle behind—now only three feet away from her loins, and inching closer by the second. Even more worrying: another, slightly larger bulge had formed at the base of that same tentacle, and was now creeping towards Dash as well.

“Mmnmm—” Thrust. Thrust. “—hhnnnnff—” Thrust. Thrust. “—nrrrrm!”

If Twilight heard her cries for help, she gave no sign. “Oh, they don’t just live in higher dimensions, but in lower ones, too? Wow…”

The bulge was just a foot away now—close enough that Rainbow could see it wobble every time the tentacle thrust into her.

“‘See also: My Universe or Yours? The Complete Guide to Other Dimensions.’ Oh man, I need to read that now…” Twilight began scanning the shelves.

Now the bulge was just six inches away. Three inches. Two inches. One inch.

“Mrrrrmmm!”

Rainbow’s nethers widened to their absolute limit as the mass of slimy liquid inside the tentacle forced its way through. Flowing deeper, it made the length of tentacle already inside Dash thicken and completely fill her canal, stimulating every square inch of her even further. Somewhere among the coils inside her womb, the tentacle’s tip flared open. And, after rushing down the yards upon yards of meat stuffed into Rainbow, the slime spewed out the tip. It took only a few seconds to fill the unoccupied crevices in her womb, then the thick liquid just kept pouring, inflating Rainbow more quickly than before.

“Hmmm—” Thrust. Thrust. “—hmm—” Thrust. Thrust. “—hmm…” Rainbow whimpered, watching her once-athletic figure disappear and her belly bloat larger. Even with her hind legs splaying further, her haunches still dug a few inches into the sides of her gut. It was large enough to fit another Rainbow Dash inside—and would very soon be large enough to fit two. Her shoulders lifted off the ground as her barrel continued inflating beneath her; now as the tentacles pressed down on her withers, they just squished her into her own swollen belly.

Twilight snorted. “Darn it, where is that book? It must be here somewhere...”

The first slime payload finished pumping into Rainbow—and, an all-too-short moment later, the second one began, having slid up the tentacle much more quickly. Her belly swelled even larger, without any pause, sloshing and jiggling with every further thrust of the tentacles. Already there was a third bulge traveling up the tentacle, and a fourth behind it; whatever liquid this creature was pumping into Rainbow, it clearly wasn’t going to run dry any time soon.

A stray tentacle tapped Twilight’s shoulder—then, once it had her attention, pointed at one of the book spines on the shelf. “Huh?” Twilight said. “Oh, you found it! Thank you. You’re such a polite tentacle monster.”

“Mmmnn!” Thrust. Slosh. “Mmrrrmm!” Thrust. Slosh. “Mhhhmmm!” Rainbow cried through her mouthful of tentacle, wobbling helplessly atop her inflating gut. This was completely absurd. This was utterly horrifying. This was hot as hell. The skin of her belly and lining of her womb stung blissfully as they stretched further, bloating with gallon after gallon of slime. The tentacle pumping into her nethers had swollen thick enough to brush every inch of her insides with each thrust. The one in her mouth just dug deeper and deeper into her esophagus, heedless of her muffled pleading. And the one poking playfully just beneath her tail…

Rainbow’s eyes shot wide open once again. There was another tentacle poking at her backdoor. “Nnmmnn!” Thrust. Slosh. “Nnnnnn!” she shouted around the thick meat filling her mouth, trying in vain to plead that the creature leave her last orifice unmolested. But her muffled cry went unheeded. The tentacle rammed into Rainbow’s rear, penetrating six inches deep with its first thrust. It, too, shoved forward again and again, falling into the same rhythm as the other two tentacles.

And Rainbow’s mind was once again carried away on a flood of pleasure—her eyes unfocusing, her back tensing and arching. Her body, of its own accord, tried to take in more of the tentacles, even faster: she sucked and licked frantically at the one in her mouth, and she bucked erratically against the two behind her. Rainbow’s ever-growing belly wobbled and shook even harder as she writhed atop it. Eventually, with another long sigh, she went limp.

As Rainbow returned to lucidity, the first thing she noticed was the slithering sensation on her legs and wings. The tentacles were releasing all her limbs. But by this point, the gesture was just another insult: the Green Sun didn’t need to restrain her any longer, because she was helpless to leave anyway. Her gut was swollen with as much mass as four or five adult ponies; it was as tall as Rainbow’s normal height and twice as wide. None of her hooves could reach the floor, and flying with that much weight in her belly was completely out of the question. And with every passing second, the tentacles thrust further, and more of the slime pumped into her—inflating her larger, making future mobility even more of an impossible dream. She kicked her legs—to do what, she didn’t know—and they pressed into her gut, sending ripples across its soft skin.

Rainbow could sense the tentacles penetrating her mouth and her rump—their tips burrowing deeper, inch by inch. She felt full in a way she never had before, and she grew fuller with every passing second, every inch of slimy green muscle that forced its way into her, and every new gallon of tentacle slime.

And she realized she was about to grow a lot fuller very soon: the tentacle in her mouth had a bulge now, a few feet away from her lips and sliding inexorably closer.

“Hhhmnn!” Thrust. Slosh. “Mmnnmm!” Thrust. Slosh. “Mhhhmmm?” Rainbow called out.

“Wow,” Twilight said. “This has huge implications for Meadowlark’s Second Theorem of General Magic. I hope there’s a copy of Meadowlark’s journals here for me to check against…”

Rainbow’s eyes widened as the bulge drew nearer. This payload of slime made up for its lateness with volume: two watermelons could have fit inside that bulge. “Hmmm—” Thrust. Slosh. “—hmm—” Thrust. Slosh. “—hmm…” she whimpered once more.

The payload was only a foot away, when something else made Rainbow let out a “Hmmnn?!” Deep inside, she could feel the tips of those two tentacles touch, then slide past and begin curling around each other. They had penetrated Rainbow from both ends and met in the middle.

And that’s when a bulge of slime in the rump tentacle—which Rainbow hadn’t seen because she was so focused on the one in front—reached her backdoor and began pouring through. Her stomach filled to the brim in mere seconds and began expanding. And then the bulge in front reached Rainbow’s lips, forced her jaws as wide open as possible, and proceeded to pump even more slime down her throat.

She was inflating faster than ever: her belly already held the mass of eight ponies, and more gallons pumped into it with every passing second. Rainbow glanced down at the unthinkably bloated mass of her gut, then past that vast curve to the floor—drawing farther away with every inch she inflated. She prodded her stomach with her forelegs—those hooves sinking a few inches into the ballooning, sloshing surface—as if she needed confirmation that this was really happening.

Then those hooves bounced away from her belly. Rainbow squinted and tried to flex her legs again, but they disobeyed, sticking straight out instead. Then, as she watched, her limbs began thickening. Tentacle slime poured into all four of her legs, inflating them too stiff to bend—or do anything besides waggle a few inches.

The tentacles finished emptying their first payloads into Rainbow’s mouth and rump—and new masses of slime, even larger, sloshed into their places. Still more bulges were already sliding up those tentacles, on their merry way to inflate her even further. And all the while, the tentacle in her nethers kept busy, spewing payload after payload, dozens of gallons at a time to bloat her ever larger.

“Aha!” Twilight said. “Here we go—Meadowlark’s Journals: The Greatest Hits. Normally, I’d prefer the complete anthology, but under these circumstances, the abridged copy will suffice.”

The liquid was filling Rainbow’s whole body now. Her haunches ballooned bigger than a pair of beach balls and began swallowing the bases of her legs. As her whole body sloshed, her expanding rump cheeks wobbled and slapped each other lewdly. Her back was softening and rounding out; as Rainbow tried to clench her wings, they squished a few inches into her sides. And then she couldn’t clench her wings anymore. Of their own accord, they unfurled and stuck straight up, filled with slime until they were as stiff as her legs. Then, with a Sloosh! Sloosh! Sloosh! her feathers inflated, bloating one-by-one into oval balloons.

As Rainbow expanded to four times her old height and beyond, she spread even further horizontally—closer and closer to Twilight. But all the while, Twilight faced away, completely absorbed in her book. She was so close, yet so oblivious to her ballooning girlfriend’s plight, unaware of the slime-stuffed bulk swelling ever nearer. Until Rainbow’s inflating side brushed Twilight’s rump. “Huh?” Twilight said, glancing up from her book but not yet turning around. “What’s that?”

“Mmhhh…” Thrust. Slosh. “Nmmm…” Rainbow mumbled weakly, making another effort to get Twilight’s attention. As she inflated larger and pressed harder against Twilight, she could feel the side of her belly squeezing around Twilight’s shapely (but comparatively tiny) posterior.

“Oh, a cushion!” Twilight said. She leaned back, squishing her butt further into Rainbow’s soft gut. “How convenient!” She rubbed back and forth to find the most comfortable spot, sending more ripples across the surface of that expanding belly. Once Twilight was satisfied, she went right back to reading.

And Rainbow could feel her stomach squishing against Twilight’s rump, embracing every curve and crevice of that purple backside. “Hrrrm?” she wondered.

Meanwhile, Rainbow was growing rounder the larger she inflated. Before, she’d been a massive belly with a miniscule pegasus attached on top; now, she was an enormous water balloon with some appendages. Her hooves were swollen to twice their normal width and sinking into her even thicker cannons, which in turn were being slowly engulfed by her expanding torso. Her wings were thicker still, with feathers like swollen fingers, growing softer and blunter with every ounce of slime filling them. Her ass was so large, each cheek was a globe inside which Twilight could have comfortably stood up and spread her wings. Her cutie mark stretched along with her haunches; the cloud on her mark was already large enough that the old Rainbow Dash could have used it for an afternoon nap. But the largest of all was still her belly: stuffed with dozens of times Rainbow’s mass in slime and tentacles, it lifted her to six times her old height, and even higher.

Twilight read aloud: “‘For more information, see Everything You Ever Wanted to Know about Alternate Timelines (But Were Afraid to Ask).’” She stepped away from Rainbow to slide her book back into place, and she scanned the bookshelf. “Hmm… Now where’s that one? Oh, it’s on the top shelf! It’s so high! How will I ever get it down?”

Twilight looked around, and when her gaze fell upon Rainbow’s expanding bulk, her whole face lit up. “Of course!” she declared. She pranced right over, crouched next to the blue balloon, then leaped as high as she could. At the top of that arc, Twilight glomped Rainbow’s side and clung there, and the slime-filled mass sloshed from her impact. Then Twilight climbed up. As she ascended, her hooves squished deep into Rainbow’s bloating form, squeezing bits of that belly between her hind legs and against her own stomach. At last, after much shaking and sloshing and rubbing together, Twilight climbed past Rainbow’s hooves—the only part of her legs that hadn’t been engulfed yet by her torso’s expansion. Here, atop Rainbow’s withers, Twilight could stand up.

“Now I can reach it!” She reached out and plucked a book from the top shelf with her telekinesis. “This is so convenient.” She sat down, her hooves and rump sinking a few inches into Rainbow’s inflated back, and opened her book. But as she continued reading, she kept glancing around.

The bloating form of her girlfriend lifted Twilight nine times her height above the floor, and higher with every passing second. But even from this high perch, the twin balloons of Rainbow’s rump towered over her. Each of those cheeks—still shaking and lewdly slapping—could have been a cushion large enough for (normal-sized) Rainbow and Twilight to make love on. And Rainbow’s wings stuck up higher still. The largest feathers were as tall as one of Applejack’s trees and as thick as a cider barrel—while even the smallest were the size of a kayak, but blunt and round.

With a wry smile, Twilight scooted over to the nearest of the smaller feathers, one of Rainbow’s interior coverts. She lifted her tail and backed into the feather, lying down with her rump planted against that tall, blue balloon. In that position, Twilight resumed her reading.

Rainbow inflated to ten, eleven times her old height. As she filled even wider, her bloating gut brushed against the stone wall on one side and the bookshelf on the other side. Her hooves sank deeper into her expanding sides; only a few inches of those thickened limbs still stuck out. Her neck had likewise disappeared into her body, and now her bloating shoulders bulged over the base of her jaw and brushed the back of her ears. Once more, she tried to call out to Twilight: “Hrrrmm…” Thrust. Slosh. “Nmmm…” Thrust. Slosh. “Mrrmm…” Rainbow’s muffled voice was so weak, she just had to hope she was audible over the constant background noise—the squishing and slurping as the tentacles relentlessly thrust into her, and pumped her with endless volumes of slime.

Twilight flicked one ear at the sound. Then she flexed and relaxed her haunches, brushing her backside a few inches up Rainbow’s bloated feather, then back down. She repeated it slowly, casually rubbing herself against that tall blue balloon as she turned a page and continued reading. The feather pushed back—pressure building up inside as more slime inflated it larger—and it squished tight against Twilight’s nethers.

Rainbow wanted to cry out one last time. Her sides completely engulfed her hooves, a harbinger of what would soon happen to her face. Her head was sinking deeper into her torso, her ears pressed tight against her skull and her cheeks squeezed between her bulging shoulders. If she couldn’t get Twilight’s attention before she was swallowed up by her own inflating body, then Twilight would never hear her! But when Rainbow tried to raise her voice, the bubbling cocktail of sensations in her mind—the thick, meaty tentacles invading her every orifice, filling every space within her, beyond all rational capacity; the stinging of her skin as it stretched to contain endless volumes of liquid; the pressure as the stone wall pushed back against her bulging belly, as the edges of the bookshelves dug into her squishy mass; her confinement within her own body, with her legs sunken beneath her bloated torso and her wings too full to move; and the quickening motions against a single one of her inflated feathers, as Twilight pleasured herself, apparently unconcerned with Rainbow’s ballooning plight—was just too overwhelming for Rainbow to put any force into her cry.

Twilight’s grinding was faster now, more erratic. She bit her lip and lifted her head back, not even pretending anymore to read the book in front of her—which was bouncing up and down atop the wobbles from her hip-bucking. She panted loudly, another voice for the obscene chorus of slurping and sloshing that heralded the continued inflation of the pegasus underneath. Finally, her back tensed, and she grabbed and squeezed—the swollen feather between her hind legs, and as much of Rainbow’s bloated back as she could fit between her forelegs. She buried her face in the mound between her fore hooves and breathed out, before at last relaxing.

Rainbow inflated to over fifteen times her height. Her bloated primary feathers brushed against the ceiling, bringing down a slight shower of dust. Her wobbling rump cheeks were large enough to house a small family. Her massive belly already covered most of one wall and most of the bookcase, and now began to press against the other two walls. Her shoulders bulged over her head further; only her muzzle was exposed now. From there, Rainbow’s field of vision was restricted to a circle only a few feet wide, directly in front of her snout.

“Aha!” Twilight proclaimed from somewhere above. “I’ve got it!” She took to the air and hovered a few feet in front of Rainbow Dash, right in Rainbow’s line of sight. “I finally have what I need to banish that filthy tentacle monster and save my dear Rainbow Dash!” She spoke with the voice of an angel, and Rainbow almost expected a hole to spontaneously appear in the ceiling so a sublime light could shine down upon the alicorn.

Twilight looked straight and Rainbow and said, “Hmmm…” She scanned the rest of the room. “That’s odd.” She looked back at Rainbow. “Very odd. I finally figured out how to rescue Rainbow Dash, and now I can’t find her anywhere! All I can find is this huge, blue balloon…”

And that moment was the last thing the pegasus saw. Soft, squishy darkness took Rainbow Dash, as she sank completely into her bloating torso. But she wasn’t really Rainbow Dash anymore, was she? Twilight had said so—she was just a balloon. And balloons couldn’t move on their own, or escape, or cry for help. All they could do was inflate, bigger and bigger, so that’s what she would do.

And, apparently, they could have mind-blowing orgasms, as she was finding out first-hoof.

—————

Meanwhile, Twilight landed once again on Rainbow’s swollen form, this time clinging to her bloated shoulders. She held one ear right next to the divot where Rainbow’s head had been engulfed, listening intently for her girlfriend’s muffled voice—and through the gallons of slime, she heard the telltale moans of one very satisfied pegasus. With a thought, she wafted a bit of magic over to the Green Sun, instructing it on just where to stimulate in order to draw out Rainbow’s last orgasm for as long as possible.

She wore a warm smile as she brushed one forehoof against that sky-blue coat, tracing a small circle on that swollen shoulder. She could feel the liquid pressure building up inside—feel her girlfriend continue inflating even in the throes of her climax. It warmed Twilight’s heart—not to mention other parts of her body—almost as much as Rainbow’s ecstatic moans did.

Rainbow gave one more, very extended moan, then went silent. She was finished.

“Red!” Twilight shouted.

For a second, all was still. Then, the previous sounds of thrusting played in reverse: the Green Sun retracted all of its tentacles, pulling yards of their thick, green flesh out of Rainbow’s orifices. With a wet pop!, the tips came free, then zipped back to the book and disappeared into its illustration. The book (hovering in the one corner of the room that Rainbow hadn’t spread over yet) snapped shut by itself and fell to the floor, and the green aura faded to nothing.

With the mass of the tentacles removed, Rainbow’s diameter shrank a few feet, but no more. Every last drop of liquid stayed inside her, although she was jiggling even more than before—upon the Green Sun’s departure from this plane of existence, all of its slime had transformed into ordinary water.

Still, Rainbow remained a sky-blue blob of a mare: a belly nearly twenty ponies high and twice as wide, touching all four walls of this room; in-folded pits where her head and legs had been swallowed by her torso; a rump so thick, it could probably destroy a three-story building; and bloated wings that threatened to punch holes in the stone ceiling above.

“Come on, my big balloon.” Twilight’s horn flared. A blinding flash of magic filled the room—then the pony and the massive blob who had been a pony both vanished.

—————

Excerpt from 1001 Spells and Incantations for Carnal Pleasure (1st Edition, copy recovered from a hidden library in the Castle of the Two Sisters):

The Green Sun

An otherworldly, incomprehensible intelligence from a higher dimension of pure pleasure, the creature nicknamed The Green Sun wants nothing more than to show ponies a good time! He possesses a complex number of tentacles, and his lovemaking skills with them are beyond mortal comprehension. A natural empath, he will vary his technique to give you exactly what you want, without you needing to say a thing: slow or quick, gentle or rough, vanilla or kinky. (Of course, if you’re making love with a tentacle creature, you’re already pretty kinky!)

He responds to safe words, either verbal or mental—preferably the standard “Red”, “Yellow”, and “Green”. But he will follow others, provided you explain their meaning beforehoof.

—————

The sun crept lower in the sky, but a few hours still remained until nightfall. Twilight and Rainbow had plenty of time to get back to Ponyville before the Everfree became dangerous.

The two were now in the Castle’s out-of-the-way courtyard, parked in front of a fountain. Twilight held Rainbow’s tail in her telekinesis, cranking it up and down like a pump handle—and with every pump, water poured out Rainbow’s mouth, into the fountain.

At last, Twilight finished pumping, and Rainbow—almost completely restored to her normal shape—sprawled in the soft grass at Twilight’s hooves. So the alicorn bent and began massaging Rainbow’s back, starting with her withers and working down.

“Mmmmmmm…” Rainbow said, “that feels goooooood…”

“Glad you like it.”

“Wait a sec…” Rainbow glanced down and finally noticed the one thing that hadn’t gone back to normal. Several gallons of water still remained in her belly, slightly squished underneath her, and jiggling as Twilight’s hooves worked her back. “Twi, you didn’t deflate me all the way!”

“I know.” Twilight unfurled Rainbow’s left wing and began preening it, running her snout down the first column of secondary feathers. “You look cute with a bit of a paunch.”

Rainbow blushed and tilted her ears back. “No, I don’t!”

“Yes, you do.”

“No, I do not look ‘cute’! I’m ‘cool’, ‘awesome’, and ‘radical’—I’m not cute!”

“Princess Celestia agrees with me that you’re cute. That makes it official.”

“No. You did not tell Celestia that.”

“I wrote it in one of my friendship reports.” Twilight poked Rainbow’s water-filled paunch with a hoof. “‘Dear Princess Celestia, today I realized that Rainbow Dash is the cutesiest-wootsiest pony in all of Equestria. I just want to state that for the record, since I’m pretty sure you’re going to preserve these letters for all eternity. Your faithful student, Twilight Sparkle.’ Yeah, I’m pretty sure I wrote that.”

Rainbow snickered. “Fine. But if I’m cute, then you’re a dork!”

“Oh, dear. However will I live under this dreadful curse of dorkitude?”

Rainbow prodded her own gut. “And I’m not going back into Ponyville looking like this. You’re gonna fix it before we go back.”

“Of course.” Twilight released the wing, allowing Rainbow to fold it back to her side. “Your cuteness will be our little secret.”

“Such a dork…”

Twilight began preening Rainbow’s right wing. Half a minute passed in peaceful silence, then Rainbow spoke again. “Hey, can we take that purple book back with us?”

“Sure.” Twilight paused her preening and gave Rainbow a lecherous smile. “Did you have something in mind?”

“Well, I’d kinda like to see you inflated that big, Twi.”

“Sounds like fun.” A brief pause, and then Twilight added, “Bet I can inflate bigger than you.”

“Oh, is that a challenge? It is on!”

Author's Note

Here's a fun drinking game: Read this story, and take a drink every time I use the verb "thrust", or any of its conjugations. And by "drinking game", I mean "death by alcohol poisoning".

I hope I didn't screw up consent too badly in this one.