Celestia was happy.

How could she not be, after coming this far?

Or she was horny. The two tended to intertwine with each other.

She basked in the afterglow of her accomplishments, the success that she had found in swaying Equestria to her side.

They were here with her now, all around her. They were serving her. They were loving her. They were awaiting her.

“Creatures of Equestria!” she announced, and her voice carried across the mountainside to all of her devout followers.

They cheered for her, and she felt their countless hands upon her.

“I am grateful for all of you showing your affection for me as your ruler, your princess, and, of course, your breasts!”

They were all thankful for that. There was more than enough breast to go around. The sprawling fields of flesh extended down the slopes of Mount Canter. The exact acreage had not yet been determined—everypony who tried gave up before long and threw themselves upon her. Even further beyond, the landscape of Equestria was still nothing but white, flooded with a never-ending tide of milk to keep its citizens from knowing any concept of hunger ever again.

“I have given you much!” she called, “And now it is your turn to give back to me!”

And so they did, with gusto. They grabbed, they squeezed, they groped, they pushed, they kneaded, they loved. Every creature in Equestria all at once, crammed together, crawling over her, caressing the pliant surface. It was more than a single pony could know what to do with, but by now Celestia had grown used to it. It had her tantalizingly on edge. There was only one thing she could do to make it even better. She placed her own hands upon her bosom and ignited her horn, letting her magic flow through her so she could—

“SO THIS IS WHAT YOU HAVE BEEN USING MY REALM FOR?!”

The voice boomed like thunder across the plains of cleavage. Ponies scattered in terror, which meant, most importantly, that they were no longer providing her with the stimulation she desired. All the same, she felt more terror than outrage when she looked up.

There was a moon in the sky. Absolutely infeasible—there should have only been her sun! What’s more, though, the pale sphere appeared to be trembling. Cracks were forming in its surface, like an egg soon to hatch.

And then something emerged, the lone globe replaced with two, dark blue with a mottled spread of black and white crescents on either side. The masses were much like Celestia’s own, but they were the forbidden assets, the lower half that had been banished from the world for so long. Only faintly could she identify the pony they were attached to at their epicenter, the furious mare with a mane and tail full of stars.

“IF YOU TRULY BELIEVE YOURSELF SO ACCOMPLISHED,” Luna bellowed, “LET US SEE HOW YOU FARE AGAINST THE MASTER OF DREAMS!”

And then she leapt from the husk of the moon, and in midair she turned, bringing about her ass cheeks to the fore, descending upon Equestria like a pair of meteors.

Celestia only had moments to spare to prevent the imminent extinction (or ass-tinction) event from occurring. She shouted, exerting a glorious war cry, as she heaved her chest upward, bringing her breasts along. The enormous mounds parted with the earth and leapt upward to stand in the way of the collision. Luna came slamming into her, continents of breast and ass meeting with each other. The mountain was smothered, Celestia included, but it was a momentary calamity, as the arousal prompted a gush of milk to erupt from her nipples like twin volcanos, forcing her attacker off of her.

“I SEE YOU ARE STILL JUST AS MUCH OF A LEAKING MILKBAG, SISTER!” Luna shouted while she hovered in place, her wings inexplicably carrying her aloft in spite of her utterly gargantuan mass.

“And you’re just as much of a loudmouth!” Celestia replied as she too ascended—it was several seconds after she had left the ground that she was actually high enough to raise her breasts into the sky with her. “Or did you learn how to speak through flatulence?!”

“YOU LACK THE APPRECIATION FOR MY REFINED TONGUE!”

“Well why don’t you put your tongue between my thighs and we’ll see how refined it is!”

“YOU WOULD NOT KNOW THIGHS IF THEY BIT YOU ON THE CLITORIS!”

They swung at each other, twisting about their bodies to bring their overgrown extremities colliding with each other. They tumbled through the sky, lacking any sense of elegance in the midst of their brawl, not that they could have managed much with the ballast they were carrying. They cried out fervently, but each blow was additionally punctuated by groans of desire. The sky flashed chaotically with each clash of the sun and moon, filling with a light more beautiful and terrible than anypony had ever known.

= = = = =

Celestia was tired.

She was numb.

She was horny.

She was always horny.

Everything was horny.

Everything was breasts.

The alicorn stretched out her arms, desperately attempting to wring the soreness out of them, and unavoidably her hands found themselves prying into the softness that billowed from her chest. Her jaws gaped in a silent groan as the stimulation further disrupted her drowsiness, and she arched her back. Even her hooves pressed into the undersides of the titanic mounds when she stuck them out far, kneading herself four times over. And that was in addition to the far distant points of contact all around her—she certainly couldn’t see them, nor could she grasp enough sense of scale to judge where they were.

It wasn’t that she was tired of being aroused. It was as if the arousal itself had grown tired. Like a bottle of soda that had been left to go flat, sweet but no longer fizzing. She felt the surges that ran through her skin, along frayed nerve endings, and it filled her brain, yet it no longer provided the numbing pressure that would erase all awareness of the world around her. At least, awareness that wasn’t breast-related, the one thing that mattered the most.

Celestia made an attempt at movement. It was not nearly as easy as she remembered it being—the reason that she had thought it would be easy eluded her. She managed to stand with some concerted effort, all the while conscious of the tugging on her chest; it wasn’t exactly pleasant, but pain was just another kind of impulse to her. Trying to step down from the dais immediately proved far more difficult, as she found herself walking straight into the wall of her own bosom, and pushing into that was about as effective as pushing on a wall of brick and mortar. It brought yet more pleasure, seeping upward, and dimly she felt that the spark was reigniting, the old sensation being forced out by the new, fresh grease lubricating the internal machinery of her body.

Walking wasn’t getting any easier, however. She was still trying to push along boulders that outsized her several dozen times over. The attention of her adherents likely wasn’t helping either, pushing and shoving against her erratically. Perhaps she could have asked them to stop, but that didn’t seem like it would be particularly productive. She couldn’t have less stimulation. She needed to have more.

More.

More.

MORE.

Her tongue was lolling out of her mouth as she pressed her hands on her bosom and channeled a spell that had become so commonplace for her that she didn’t even need to think about it, it was as natural as breathing. The searing light grew brighter. She fell into herself. Her wings fluttered involuntarily. The flesh pushed back against her. It surged all around. Some ponies went under, swallowed up by the tide. It didn’t stop any of them from continuing to grope at her, even encouraged them further. The fervor had been renewed.

And she dimly noticed something. There was a flat, hard surface, akin to the floor, except this was on either side of her breasts. It elicited delight in her, inexplicably. This called for celebration. And celebration could only mean one thing.

Yet before that impetus could take hold, Celestia found herself trying to walk forward again. It was just as fruitless of an endeavor as before, if not even more so. It was invoking introspection, something that she had not allowed herself to consider in what seemed like an inconceivable span of time. Her ears perked, attempting to take in the sounds of her surroundings, but she could barely hear herself think over the ubiquitous churning of milk and the chorus of vocalized excitement. In spite of her electrified state of mind, the hairs along the back of her neck were standing on end, gooseflesh rising on her arms.

Something was coming.

Then there was a banging on the door, a rapid-fire battering ram.

“CELESTIA!”

That terrible voice. It had followed her from her dreams, the nightmare come to haunt her in the waking world. She found herself hugging her bosom not because it made her horny but because it was something that could hide her (the thought that the breasts themselves made her presence very obvious didn’t occur to her).

The entryway came open with a slam, and the bloom within the throne room flickered. Darkness was pouring in like billowing clouds. No, not quite—it was light of a different sort, calm and soothing, ambient rather than pervasive. And there in the center of the opening there was a pony standing, nearly knee-deep in the flood of milk that was pouring out. Though her whole profile could be identified, there was so much more that sprawled out behind her, extending beyond the frame that was offered by the doorway, a canvas of blue and black.

“This has gone on long enough, Sister!” Luna shouted, booming through the hall.

The loyal ponies who once would have fought her back tooth and nail were now too drunken on breasts—either their princess’s or their own—to do much of anything to oppose her.

Celestia herself couldn’t do much either while she was so thoroughly anchored in place. She could barely bring herself to peer over the top of her white-furred fortress walls. “G…go away!” she cried weakly through the haze that was still threatening to consume her thoughts. “You…y-you don’t belong here!”

“Last I checked, Celestia, this was supposed to be our throne room!” the other mare spat, seething. The light surrounding her seemed less and less peaceful, swirling like ethereal tendrils.

“This is the Chamber of the Sun’s Repose!” she insisted in turn. “There is no place for the moon here! Be…begone, you and your ass! You can’t even fit in here anyway!”

Luna only sneered before she began to stride forward without the slightest hesitation.

The mass behind her clung on, unable to fit through the doors. So the doorway broke, crumbling to pieces, and then the whole rest of the wall followed. Panic arose as ponies broke from their stupor to run, seeking out another exit—many settled for simply burrowing underneath Celestia’s breasts for protection—as the rubble of marble spilled across the floor. Even that, though, was only a premonition for the advance of ass flesh, a new living wall that approached, swallowing up what little floor space was left in the room, a barge skating through the sea of milk. Luna’s hips ground against the walls of the throne room on either side as she walked down the center of the floor, while her buttocks rose high above her head, mobile hills of blue and black fat.

“What will you do now, Sister?!” Luna called out to her, looking up undaunted at the valley of cleavage, deep and wide enough to fit a train car or two within it.

“I…how…how could you do this?!” Celestia asserted indignantly, feeling some semblance of authority breaking through the all-consuming arousal. If only she could muster the leverage necessary to move. “You have…defiled this hallowed space with your rump! You would dare to—”

But Luna rolled her eyes and lit her horn with a pulse of magic.

The instinctual urge to prepare defensive spells rose in Celestia’s mind. It proved to be ineffective, however. There were no offensive incantations heading her way, instead she felt the magic encompassing her whole body. She still might have managed a counterspell were it not for the tingling touch upon her skin prompting another pulse of stimulation that wracked through her brain at just the wrong moment. It wasn’t levitation, however, not moving her physically. The cyan light was closing in on her, squeezing, pinching.

She managed to gasp before her perception collapsed in on itself as she was teleported.

A moment later she was in reality again. Her hooves were unsteady, though it wasn’t exactly like she could have fallen very far, either into her bosom or held up by it, keeping her anchored. Uncertainty as to her location flashed through her mind, but she realized that the walls and ceiling around her were familiar, the same marble that she was used to seeing throughout the palace, and she was standing in a lake of milk—her own, she knew (with some of it contributed by her buxom followers). Her breasts were no longer in the same comfortable position, not sagging down along a slope, instead she felt that they were resting upon a slope, parted to the sides, of course with many ponies still smothered beneath her.

She was now facing toward the dais with the throne instead of standing upon it.

Which meant that—

“Hello there, Tia,” came Luna’s venomous voice into her ear.

Celestia’s attempt to leap into movement was halted by arms clamping down on her, pinning her own to her sides in the process, and her wings were forced flat against her back. She yelled and squirmed, but it was to no avail, Luna’s grip around her was ironclad; she had always physically been the stronger of the pair, the one more suited to feats of combat and athletic prowess—that likely had something to do with how she had an easier time walking at her present size as well.

“This is more convenient, I would say,” Luna said with a dark chuckle, “so much better for us to speak directly to each other instead of shouting across the room.”

“Nrgh…! This…this isn’t fair!” Celestia growled back at her, twisting her neck about in an attempt to face her sister, “I can’t fight you like this! I can’t even face you!”

“War is not always fair, Celestia,” Luna hissed, eyes narrowed to points, “perhaps you ought to have considered a confrontation such as this before you thought it would be a prudent idea to turn your breasts into a pair of zeppelins.”

Those zeppelins were doing her a fat lot of good at the moment. She was now doubly immobilized, by the other alicorn’s hold and her own bulk. And it was made worse when she felt the probing hands renew their efforts in kneading her flesh, heedless of the intensity of the moment which was upon them. Some of them were finding themselves caressing the fields of blue and black instead, too blinded by their lust to consider that they were embracing the forsaken assets. If Luna was bothered by that, she didn’t show much sign of it.

“And it would be just like you to make this out to be a fight,” the younger alicorn then said, seething with a vitriol just scarcely contained beneath the surface, “I did not come here to fight you, Sister. I came here to put an end to this foolish game.”

The intensity and severity of her tone brought a chill running up Celestia’s spine in spite of the stimulating fire which was exerting its control over her. “Wh-what?”

“I have grown tired of this!” Luna snapped, baring her teeth, “We have become mockeries of ourselves! And for what?! So we can have the biggest tits and ass Equestria has ever known?! We are an embarrassment to our rank and title; we cannot hope to lead ponies like this!”

Celestia wanted to retort, to argue against this, but all the while she could feel the ponies who were buried by her mountainous mammaries, pulling at her with the mindless instinct of a newborn foal suckling from its mother. She should have remembered their names, there was a time when she had known every adult in Canterlot, but she could scarcely even recall the faces of the ones she had anointed. They all blurred together into a miasma of features, a sea of flesh, drowning in milk. This had been acceptable for her position as their idol of worship, substantially less so for a princess. “What are we to do, then, Luna?” she asked, wary of what the answer might be. “Give up and return to the way we were before?”

But that prompted Luna to laugh. “As if! I could never dream of being rid of my posterior at this point! Just as I doubt you would ever part with your bosom.”

“Well that’s one thing we’re in agreement on at least,” Celestia remarked dryly, “then what solution do you have in mind?”

“The fighting needs to stop, we can no longer afford to quarrel amongst ourselves about whether breast or buttock is superior.”

“Very well, then we can…not do that.”

However, Luna only gripped tighter, squeezing without relent. “It is not that easy, Sister; you forget that we have a host of ponies following our commands. They have already been set on a course for destroying each other, they will continue their ways with or without us. The whole disease must be contained and crushed before it can spread further. And it just so happens that you have allowed yourself and your followers to become too drunk on the high of orgasm to do anything about it.”

A chill ran up Celestia’s spine at the implications of what was being suggested to her. “Luna, what’re…you can’t be planning on…!”

“Nothing so grisly, Sister,” Luna replied with bitter finality, “I will simply have to remove the source of your cult’s worship, as well as the favors you have bestowed.”

The realization of what that statement meant was far worse than anything she had been imagining before. “N-no, you—! You can’t! You can’t do this!” She flailed with renewed vigor, but still to no avail. “You can’t take my breasts away!”

Luna scoffed harshly at her. “Do not attempt to play at my heart strings. I know that you would have said the same to me if you had had the opportunity, were you not so fixated on immediate gratification!”

“What?!” Celestia snapped back at her indignantly, “Don’t insinuate that, I would never—”

“DO NOT LIE TO ME!” the younger alicorn yelled, deafening, right into her ear, her voice rumbling with power and a flash of moonlight filling her eyes. “I saw your dreams, Celestia! I saw how you reveled in a world in which you were rid of me! Do not pretend that it did not happen!”

She gaped and her attempts to struggle went still all at once. “L-Luna, I…that…that was just a dream, I didn’t…I wasn’t really going to…”

“In somno veritas, Sister,” Luna growled. “If there is one thing I have learned, it is how to glean the deepest desires of a pony from seeing their dreams. Maybe you do not wish to do it now, but the impetus is there in you, just waiting to take root!”

Celestia wanted nothing more than to deny this, but she found that she could not. She loved her sister, and yet she found that there was a great deal of evidence to suggest that she had not been taking that into consideration for the past few days (she actually found herself struggling to remember the exact passage of time, uncertain if it had been days, or weeks, or months since this all began). She had set her followers against those of Luna, insisted that Luna was a temptress not to be trusted, that to be allied to her was tantamount to treason. And for what? She could not recall the reason—the reality was that there had likely never been a reason. Not a real reason, at any rate, a reason founded in basis of fact and logic. It was because she had felt threatened by Luna’s growth. And because she couldn’t contain her hunger for growth. Envy and excess in tandem, pulling her down a path to sin.

She would have welcomed her punishment, knowing fully well that she deserved it for her part in exacerbating their conflict.

But she could never possibly welcome the idea of giving up her breasts.

“It will take but a moment,” Luna said grimly, “I already practiced the spell I will use.” A horn lit up with a shine of magic.

“N-no!” Celestia twisted and writhed anew, with all of her strength, but there was still nothing she could do to get away.

“There is no point in struggling!” Luna asserted, her magic channeling more intensely with each passing second. “If you are so concerned with your ability to constantly be a hair’s breadth from orgasm, I will permit you to be just as excessively bottom-heavy as I am once we are through!”

Then an idea formed in Celestia’s mind. It was crazy, but it would have to work. She had mere seconds to pull it off. She twisted her arms, reaching behind her back, in between the two of them.

“This is for the best, you will thank me for it eventually,” Luna insisted as her spell neared completion.

“You’ll have to thank me for this first!” Celestia interjected, and her horn flared with sunlight immediately—for though her sister was physically stronger, her magic had always been superior—as her fingers touched the soft swell of Luna’s chest.

Promptly, something pushed back against her, accompanied by the sound of tearing cloth.

“Wh-ah-AH!” Luna’s exclamation morphed into a gasp and then a cry, all while her hold on the other alicorn loosened.

A bolt of magic fired from her horn, flying wildly up toward the ceiling, fizzling without effect.

Before Celestia looked back, she already heard Luna’s labored, panicked breathing, tinged with a mounting undercurrent of arousal. The blue alicorn was staring wide-eyed at her chest, which had obliterated the top she’d been wearing in the process of growing to the size of a pair of basketballs, hanging over the upper reaches of her stomach. Miniscule, of course, compared to her rump, or to her sister’s breasts, but certainly a dozen cup sizes or so up from what she had been before. She held her arms far out to the sides, as if she didn’t dare touch the heavy globes even for a moment. “You…wh-what…?!” she stammered, only to freeze up when she saw her breasts jiggle, trembling with every slight motion that she made, even breathing, steadily rising and falling. She managed to level her gaze upon Celestia, eyes quivering with a mixture of emotions, rage and confusion and disbelief.

And Celestia found that she could only chuckle, a smirk curling across her muzzle. “It’s okay, Lulu, there’s no shame in admitting that you like it,” she said, and she patted the side of her own breasts, “just give yourself a feel and I’m sure you’ll—”

Luna lunged forward. “Feel this!” she shouted as she grabbed the white rear in front of her.

Celestia didn’t get a chance to react before the mana pumped into her.

The swelling of flesh was a sensation she had grown well-acquainted with, but it was entirely alien for her to feel it centered in her lower half. There was something different about it; it felt meaty, in a sense. Not that she had much time to reflect upon that as the process was almost instantaneous, the jolt of momentum pulling her backward momentarily. She was suddenly all the more conscious of the sensation of skin pressed against skin, buttocks and thighs rubbing together. Her balance might have been upset more if she weren’t already weighed down by her breasts. It wasn’t so easy to crane her head back and gauge her exact size, but the fact that she could see so much of her ass, fields of white parting the folds of her skirt, was indicative enough by itself.

“Uh…oh…” she muttered as she placed her hand upon the slope of her hip, over her sun cutie mark, fingers sinking into the pliant flesh.

“I am sure that you will enjoy yourself, Tia,” Luna jeered back, sneering, crossing her arms over her chest, though briefly appearing flustered at the way this made her bosom compress.

“O-oh…” Celestia didn’t seem to hear her, however. Her hand was probing further around the circumference of her buttock, hefting the mound of flab that was like a padded cushion grafted to her rear, then down along her thigh. She arched her back as her spine tingled with electricity.

Luna stared and blinked. “No, Celestia, I did not mean that you were actually supposed to enjoy it.”

“Luna,” she spoke, not truly hearing what had been said, “why didn’t you tell me that this felt so good?”

The younger alicorn’s disbelief intensified. “Did you think I would have done this to myself if I had not liked how it felt?” she asked while reaching back to pat at the blue wall behind her.

“Oh, it’s so…juicy!” Celestia now used both hands, squeezing on either side of her buttocks while she slowly gyrated her hips. “The way they swing! It’s lovely!”

“Celestia, you cannot just…!” But Luna gave up on her train of thought, not knowing what to say. Was she supposed to be angry that her sister shared in her appreciation for big asses after all? No, that was ridiculous, even if it made the whole scenario a tad anticlimactic.

But she knew what this meant the appropriate follow-up action for her was, and she grimaced at the thought of that. She looked down at herself, a view which was now mostly tit, occluding everything beneath. She hesitantly held her palm up toward the blue curve and grumbled, “What could possibly be so delightful about—” Then her fingers touched at the bare dark skin of her nipple, and she yelped at the tingle that coursed through her. “Oh…that…” Her musing gave way to restrained moaning as she cupped both overflowing breasts and squeezed each nipple. Faint beads of white emerged from the bumpy flesh.

“Tia, this is…why does this feel so good?” she crooned while pressing the mounds flat against her chest.

“One of the miracles of life,” Celestia replied, belting out a laugh, “just like this ass.”

“Oh, gods, I cannot fathom how I failed to indulge in this for my whole life,” Luna moaned, her tone turning increasingly passionate.

The atmosphere of the packed and wrecked throne room was growing increasingly heady as the two alicorns fell deeper into arousal. Their very presence, the two of them combined, emanating an intense aura of sexual pleasure, was prompting several ponies packed into the crevice between the behemoth breasts and buttocks to spontaneously fall into throes of orgasm all at once.

“Tits are…rather splendid,” Luna mused plainly.

“Having a nice ass isn’t too bad,” Celestia added.

“Oh, Tia…I don’t know how I let this come between us.”

However, when Luna then moved to wrap her arms around Celestia in a far gentler embrace, she was met with resistance when her newly enlarged bosom mashed against the white alicorn’s wings and back, while her own rump pushed backward and blocked her sister’s pelvis.

“I suppose it’s understandable that there was some resistance to overcome,” Celestia replied with a smile, and she reached back, stretching to place a tender hand upon Luna’s cheek.

They both laughed softly and pressed inward to complete the embrace, the pliant girth compressing between them as they nuzzled with each other.

And Luna whispered, “You are thinking the same thing as I, I hope?”

Celestia grinned. “That it’s silly for us to be so uneven at this point?”

“Yes, I concur.”

“Let’s fix that, then.”

While they were channeling their magic into themselves, they were already working up their imaginations at the idea of what might await them. With two princesses unified in their love of tits and asses, it would be so much easier for them to manage their loyal followers, bringing them together for a mutual appreciation for immensity. Both of them could so easily imagine themselves, now sporting equal gargantuan proportions in both their upper and lower bodies, towering above the populace, their audience waiting with rapt attention for what decrees they might dole out. They were practically drooling, on the verge of climax, already feeling the phantom sensation of their taut flesh, so gloriously burgeoning, straining the definition of their forms. Celestia thought of the titanic rump which she would drag behind her, the most heavenly mattress which she could recline upon whenever she desired. Luna envisioned the bloated blimp breasts and the rivers of milk which would flow from her at all times. The light of the sun and moon blazed all around them as magic suffused their bodies, resplendent and radiant.

Neither of them took a moment to consider that they were positioned front to back with each other, or that they were already filling the throne room well beyond its maximum capacity.

They would later rationalize this by saying that they had outgrown the need for the palace anyway.

All they needed now was their girth and each other.

Author's Note

And so we come to the end of all this and the serial escalation reaches its peak. One of the biggest issues I was wary of throughout the whole thing was not wanting to err too hard on either one of the princesses objectively being the one in the wrong, just acting selfish amid misunderstandings. In the end, though, it ended up being that Celestia was, ironically, a lot more of an ass than Luna. Perhaps doesn't help that she got way more of the obligatory "sexual stimulation mindbreak" end of the stick so she's way more out of character. Oh well.

At one point the story would've ended with Twilight showing up on a friendship mission and telling off Celestia and Luna for being stupid but by the time I got to that point I felt that would've just overcomplicated things and did something different.

Surprisingly, no princest beyond light teasing.

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