The Conversion Bureau: A Thing Which Must Not Be

by Brinstar77

Rating: mature
Tags: Science Fiction, Horror, Non-consensual, Violence, Princess Celestia, Crossover, Alternate Universe, Gore, Original Character, My Little Pony: Friendship is Magic, Dark, Warhammer
Length: 3128

Captain Tuurok Castar of the Marines Malevolent has just received a crash course on why you do NOT mess with ponykind... in both the present, and a dark future that must not be.

Captain Tuurok Castar of the Marines Malevolent has just received a crash course on why you do NOT mess with ponykind... in both the present, and a dark future that must not be.

A Conversion Bureau/Warhammer crossover with a Cosmic Horror spin. Also a Grimdark brutalization fic... in which the ponies are the ones doing the brutalizing.

No explicit gore, violence, or non-consensual sexual activity, but this is all the worst elements of 40k and the Conversion Bureau combined, and non-con body modification is endemic to these sorts of fics, so tags are present just to be on the safe side.

Published 2024-11-06 08:00:00 UTC
Last updated 2024-11-06 08:00:00 UTC

The Shape of the Nightmare

Death to the xeno.

It is a creed repeated throughout the Imperium, drilled into our hearts and minds from birth, so strong not even falling to chaos can break its hold over us. That creed has served as equal parts shield and sword, guarding us from horrors untold at the hands of the Dark Eldar, the Orks, the Tyranids, and other, far worse things.

If only we’d known that clinging to it would be our undoing. And that the undoing it would bring would be far worse than any other.

Even now, my transhuman mind still quails at this nightmarish new future I have awoken to, despair snaking its way through my twin hearts every time I am reminded of my inhuman body and these unnatural hooves, reminded of the fact that I am a living monument to the horrors unfolding all across the galaxy.

If Mankind was to die, if the Imperium was to fall and darkness rule, it should have been after a desperate, heroic last stand, with the defenders of Humanity standing against their myriad foes, refusing to go quietly into that gentle night. It should not have fallen the way it did, swept aside by another nation as effortlessly as an ogryn might swat aside a mosquito, its battle cries impotent and meaningless to the mad tyrant who stripped us of everything that made us human.

I dealt with it the only way I knew how; by seeking to understand how this nightmarish new normal came to be, scouring the galaxy for any clues hinting as to how humanity had crumpled like tissue paper. To my eternal regret, I have succeeded. This, then, is the tale of how the God-Emperor of Mankind died, how the Imperium of before was burned away, how the Solar Empire rose from the ashes to crush all beneath its terrible power.

It began simply enough, with the discovery of a world by the name of Centaur III. It was a world of blue seas and green lands, possessed of a climate and atmosphere reminiscent of the Holy Terra of yore, ripe for colonization. There was one small problem; there was already life on this world. Structures were visible, human-like in their composition yet designed in a way that made it clear that their inhabitants were nothing like us.

As the Marines Malevolent company that discovered the planet would have learned had they put away their boltors and tried to be diplomatic for once, the inhabitants of the planet were horse-like, benign, and eager to make friends. Unfortunately, they chose to do what the Imperium had told them to do with any unfamiliar xenos; shoot first and ask questions later. They sent an astropathic message notifying the rest of the Imperium that they had started efforts to wipe all traces of sentient xenos off the face of Centaur III; that was the last we heard from them.

Maybe if my gene-brothers had an inkling of the consequences of their actions, had chosen to attempt peaceful contact, this whole nightmare could have been averted. Or maybe not. Our chapter was always notorious for its aggressiveness and general disdain for mortal lives; its disregard for collateral damage was regarded as egregious, even by the surprisingly lax standards of its fellow loyalists. In a way, it’s somewhat fitting that we, the living embodiment of contempt, fury, and violence taken too far, would be the ones to unwittingly unleash such horrors upon our beloved Imperium.

Details of what transpired next are scarce, the events that precipitated the rise of the Solar Empire unclear even amongst ponykind. There is a consensus that a mass slaughter of ponies — soldiers and innocents alike — occurred, but precisely who did the slaughtering is unclear. The same is true of Solaria's origins, all agree that she was somehow birthed in the fires of that three-day conflict, yet none can say how.

But I can make a guess. The Marines Malevolent may have been a Chapter reviled even by many of our fellow Loyalists, but we were still the Emperor’s Angels, more than capable of eradicating the then-primitive ranks of ponykind without resorting to the dreaded tools of exterminatus. Against such a threat, ponykind’s military would have likely been shattered and forced to retreat in very short order, leaving my gene-brothers free to hunt down Centaur III’s sizable xenos population at their leisure. With her species staring down extinction, ponykind’s matriarch, whose name has been lost to the march of time, likely called out for any being or deity willing to help. And something answered.

Three days after the company’s final broadcast was received, a ponylike xenos appeared at the borders of the Solar Segmentum, a being of unrivaled power we’d soon come to know as Queen Solaria. To call what followed a slaughter would be the understatement of the century. The seemingly insurmountable fleets of the Imperial Navy crumpled like tissue paper beneath rays hotter than the deepest depths of the brightest stars, defenses that had endured 10,000 years of endless warfare swept aside in a matter of hours. The defenders of the Imperial Palace proved no less durable, whole titan legions annihilated as Holy Terra was set alight. Not even the mighty Adeptus Custodes were able to stand against Solaria’s limitless fury, the greatest warriors the galaxy has ever seen—human or otherwise—cut down with horrifying ease.

It took all of a month before Solaria tore her way through the Eternity Gate, sundered the Golden Throne, and extinguished the Astronomicon… and it only took her that long because she opted to scour all other men, women, and children from the Holy Terra system first, saving the God-Emperor himself for absolute last.

Without the Astronomicon to guide them, millions of starships were cast off their path, lost in the Warp. Many fell to the depredations of daemons. Others emerged thousands of light-years away from their intended destinations. More still linger in the Empyrean, perhaps to be released in centuries or millennia to come… though I doubt they will last long in the galaxy they emerge into.

Days later, as ponykind counted the death toll and sought to make sense of all that had occurred, their Queen returned to them. Solaria immediately established the Solar Empire as it is today, with her as its harsh, ruthless ruler, backed by the same unfathomable power that allowed her to single-handedly decapitate the entire Imperium in a single stroke. Ponykind, badly rattled by the chaos of before and too desperate for stability to mind the loss of freedom, readily accepted her cruel dictates at first. Under her iron hoof, Equestria was reforged into an oppressive authoritarian regime undergoing rapid industrialization, quickly becoming a perverted echo of the very Imperium its ruler had just laid low. Thousands of years of medieval stasis were undone in an instant, Equestrian society pumping out new technologies at a furious pace, in spite of the fact that all of the population had been reduced to little more than slaves, fed just enough to be kept productive. Anyone who argued against the morality of these technologies consisting almost exclusively of tools of death and destruction was silenced… and the same was said of any who looked too deeply into the development of a certain transformative elixir.

With Ponykind having constructed its first spacefaring vessels in fewer years than can be counted on a single human hand, the war began. Driven by the warmongering dictates of Queen Solaria, her subjects launched a galaxy-wide campaign of conquest and extermination. All sapient beings they encountered—human and xenos alike—were offered a “Conversion Potion”, a vile concoction that transformed its imbiber’s body into a pony and their mind into an empty, soulless automaton, bound even more deeply to obey Solaria’s will than the ponies she ruled. Those who rejected the potion had it forced upon them, any who objected to the way it stripped away the imbiber's will and identity brutally purged. Not all forced to taste the vile concoction lose their identity to it—as I, a former Captain of the Marines Malevolent, can personally attest—but those ‘newfoals’ not bound to Queen Solaria’s will are as quick to be executed as those who question the morality of their Conversion.

Its ranks flooded with the willing and eager slaves the Conversion Potion created, ponykind spread across the galaxy like wildfire, Solaria’s ruthless tyranny spreading with it. Free-willed newfoals and rebelling natural-born ponies alike joined desperate survivors in fleeing the encroaching Solar Empire, bringing news of its atrocities with them, and the fragmented splinters of the old Imperium found themselves allying with increasingly-perturbed xenos as they prepared to resist.

Unfortunately, while the newfoals may have been mindless slaves, they made frighteningly effective soldiers none-the-less; all who tried to resist were crushed by the combined might of Solaria’s legions and the treachery of too many of their own, blinded by the supposed freedom from pain offered by Solaria’s Conversion Potion and failing to see the spiritual death it promised.

When the Solar Empire’s armies were stretched thin as natural-born ponies intelligent enough to command the endless legions of mindless newfoals began to wear thin, Solaria simply developed a new form of the potion, one that sometimes turned its recipients into frighteningly powerful alicorns. While just as mindless as their newfoal brethren, these winged unicorns had inherited a tiny fragment of Queen Solaria’s fathomless power, thus becoming vectors of her genocidal will, as ruthlessly capable fighters as they were leaders. By the turn of the next decade, the Solar Empire had annexed the entirety of the Segmentum Solar and a frighteningly large swath of the Segmentum Ultima, Ultramar, and its capital of Macragge among them. By the next, all space formerly held by Imperial forces was under their rule.

In the Eye of Terror, Abaddon the Despoiler watched all this unfold, with something I imagine to be adjacent to terror coursing through his veins. The Traitor Legions, long divided by internal rivalries, banded together under his banner, their Primarchs returning from their ethereal pursuits and leading their sons to war once more. And not a moment too soon; Cadia soon fell, not to a Black Fleet seeking egress from the Eye of Terror but to a pony army seeking entry, headed by a Converted alicorn once known as Ursarkar E. Creed.

Once again, Queen Solaria had done the impossible; her Empire has united the servants of Chaos, its armies giving them a common purpose strong and urgent enough to surpass their instinctual distrust of one another. The war for control of the Eye still rages to this day, fathomless legions of newfoals flooding through the Cadian Gateway and throwing themselves at the equally-endless ranks of the Lost and the Damned, united in a manner not seen since the Horus Heresy. I can’t help but wonder if that name still applies to them, given that without our God-Emperor, we are just as lost and damned as they are, if not more so.

Ahriman continues his quest for the Black Library, hoping now to find within its halls the secret of Queen Solaria’s limitless power and the means by which she may be struck down. Heretic though he may be, I find myself hoping that he will eventually succeed, that when he finally locates the ancient Craftworld its Harlequin guardians will welcome him in rather than fight to keep him out. It is a foolish thing to invest hope in, the possibility that one apathetic god may rise to replace another, but there is little else left to hope for.

The Eldar, already on the brink of extinction, have been hunted down mercilessly. Only a handful of Craftworlds remain, and of them, only Ulthwe stands any hope of enduring for more than another decade, thanks to the ceaseless guidance of their Seers. Without the protection of their Craftworld kin, the Exodite Eldar were slaughtered with impunity by the ponified legions, their World Spirits slain and their inhabitants Converted. And in their Dark City of Commoragh, the Dark Eldar are beginning to starve, slowly but surely deprived of the abundant source of torment that Mankind was to them as their numbers wear thin. Desperation is setting in as the Kabals start to turn against one another; open war is inevitable, and it will be a surprise if it doesn’t break out by the end of the year. In a thousand different sectors, similar tales are playing out, all as xenos and humans alike are forcibly assimilated into ponykind’s ever-growing ranks, or outright annihilated when this is infeasible—such as with the Necrons or Tyranids.

And of the noble Grey Knights, I have heard nothing. The final reports of the defenders of the Sol system, before the last of them were wiped out in Solaria’s rampage, indicate that Titan, their home, has vanished from Saturn's orbit. No sign of it has been seen since – nor have its transhuman inhabitants shown any sign of their continued survival. Yet Converted Grey Knights have not been sighted amongst the Solar Empire’s ranks either. In my most deluded moments, I tell myself that the last gift of the Emperor to Mankind might just still hold our last, best hope for salvation… but it is nothing more than a delusion, albeit a comforting one.

Such is the state of the galaxy now. Mankind lingers still, clinging to existence in the shadow-shrouded enclaves Solaria’s light has yet to reach. The one I have found shelter in, populated by battle brothers of every legion, united by simple survival, is far from the only one; there are similar holdouts throughout the galaxy, the Farsight Enclaves being one of the most notable. It is even rumored that Ciaphas Cain, a Hero of the Imperium before its violent end, still fights on humanity’s behalf despite having been Converted, having retained his willpower and formed a resistance movement in the very heart of the Solar Empire, fighting Queen Solaria’s cruel regime from within.

But even so, the days of humanity as we know it are numbered. Even as I write these words within our fortress-monastery, news of a ship searching the region circulates through its crowded, cramped halls, a ship bearing the unmistakable colors of the Solar Empire. They will find this place soon, but I am tired of running, and my battle-brothers feel the same. When Solaria’s mindless servants descend upon this dead world and march toward our home, we shall face them on the battlements, standing our ground until the bitter end. We will die before we let them shove that vile concoction down our throats… and we will be sure to take as many of Queen Solaria’s puppet soldiers with us as we can.

It will not be glorious, for our god is dead, and there is no more glory to be had. It shall not be useful, either—our defiance will make no difference at all, our hidden enclave reduced to just another conquest for Solaria’s ever-expanding empire no matter what we do. But I will not bow to this new god my chapter has unwittingly created, this abominable god of thoughtless cruelty and unrelenting order.

If we shall die, we shall die as ourselves. And nobody—no man, no pony, no god—shall take that away from us.

“NO!”

The undersized helmet flew from Tuurok’s hands, cracking open as its Ceramite plating shattered against his quarters’ plasteel walls.

Whatever foul enchantment gripped the Marine Malevolent shattered with it, the new, false memories lost much of their hold over the mind of Captain Tuurok Castar. But even so, the Marine Malevolent still remembered the fall of the Imperium and the rise of that… that thing. The lies that thing had tried to impress upon him were still vivid in his mind as if he had actually lived through those heretical, impossible events.

His mind was reeling, desperately trying to understand the two different sets of memories it now had, to distinguish between what the reality around him really was and the false visions that infernal relic had put into his brain, the visions of things that had never, would never happen-

“Sir.” A Chapter Serf stepped through the door, and Tuurok’s blood turned to ice in his veins. The name of the planet they were currently in orbit around came back to him: Centaur III. “The Company is ready to deploy. We merely need the word-”

“CANCEL THE DEPLOYMENT! NOW!!!” Tuurok roared at the top of his lungs, the sheer volume of his voice sending the unfortunate serf reeling backward. The scent of urine reached his transhuman senses; he supposed the unlucky mortal could be forgiven for losing control of his bladder. “We cannot allow ourselves to set foot on that planet! We do so, we sign the death warrant of the Imperium!”

The frightened serf nodded frantically, then scrambled off to relay the Captain’s new orders to the rest of the chapter, and then acquire a change of robes. Disaster averted, Tuurok stumbled backward, letting his trembling body lean against the wall for support. Both of his twin hearts were pumping at a furious pace; it took him a long, long moment to realize what was happening to him.

He, one of the Emperor’s Angels, a being designed to be literally incapable of feeling fear… was afraid. No, not just afraid; he was outright terrified. Of a frakking xeno.

Disgust and self-hatred welled up in him as he slumped to the ground, hugging his legs close to his chest, trying to reign in his emotions because he was an Adeptus Astartes, dammit, he was beyond such weaknesses as “fear” or “dread”! Right?

…right?

And yet, Tuurok could hear whispers in the back of his mind. Whispers that bore none of their usual laughter or mockery; only uncharacteristic words of comfort, and an acknowledgment that he wasn’t the only one who was afraid.

It seemed that even among the Dark Gods, the thing that Centaur III’s xeno inhabitants could become was something to be feared, something even thirsting gods dreaded with every fiber of their being.

A thing which—no matter the cost—must not be.

Author's Note

Congratulations on making it through my latest serving of Nightmare Fuel. I'd say happy Halloween, but inspiration for this struck a bit late...

Inspired by some of the darker elements of CB: The Other Side of the Spectrum, as applied to 40k.

For those of you wondering what the buck happened to Celestia, or how the thing she became managed to curb-stomp EVERYONE on Holy Terra so easily... that's a damn good question, and one that I've intentionally left unanswered. After all, horror works best when the reader is left to fill in a few well-placed blanks...