I do not own the Warhammer 40000 universe nor any of its characters. They belong to Games Workshop.

Inspired by the Dornian Heresy, by Aurelius Rex.

Gregor Eisenhorn, rogue Inquisitor of the Holy Ordos, disgraced and hunted down by his peers, walked through the corridors of his hidden lair with as much speed as he could muster. Years ago, during one of his last cases as a aknowledged member of the Inquisition, he had been wounded deeply, and there hadn't been time to heal him properly.

Now, as a price of his determination to get back up his feet as fast as possible, he could only move thanks to the exoskeleton surrounding his body, moving in response to his thoughts. Every motion hurt, and the cybernetic connection on his neck never stopped hurting, even when he was completely immobile. The only way for him to sleep was to dose himself with painkillers, and they had gotten less and less effective over the years as his metabolism grew more resistant to them, seemingly only to spite him. And even when they worked, they did nothing for the dreams that haunted him.

He had been in the middle of one such nightmare when the alarm had woken him. Something had gone wrong in the room of Uber Aemos, one of the last companions Eisenhorn had left from his days as an Inquisitor. The old data-savant had been tasked by Eisenhorn to collate the information they had gleaned over the years about their great enemy – the mysterious entity known as the Yellow King.

It had been the hunt for that creature that had driven Eisenhorn to the depths of what his brethren considered Radicalism, until they had finally cast him out. They didn't see the danger it posed - how could they ? It had taken years of finding hints in half-forgotten prophecies and warnings from seers that had gone mad from what they had seen waiting in the future before Eisenhorn himself had started investigating. The discovery that it may have had a hand in the corruption of the infamous Raven Guard had only cemented his resolve after that. But even now, after decades of using every resource at his disposal, he still didn't even know what the Yellow King was.

His best theory was that it was some kind of Warp entity of immense power, trying to manifest itself into reality by forcing its way through the barrier between the Materium and the Empyrean. That much he was reasonably certain of. It was when he tried to get more details as to its nature that things got absurdly tricky. The hints he had found had all been left by madmen, their mind shattered by what they had seen, and made no sense when put together. That was why he had Aemos, and many other scholars like him down the years, work on finding some pattern, some clue as to the entity's designs. Knowledge was power, and never was that more true than when the Warp was concerned.

There were signs of the Yellow King's influence on Humanity that went back tens of thousands of years, even before the species had developed space travel. Through the entirety of Mankind's history, there had been those who had been haunted by the image of the Yellow King and driven insane by what they saw. That seemed to indicate some kind of powerful daemon, but the servants of the Dark Gods seemed to oppose the Yellow King's manifestation, even if they interfered with Eisenhorn's work at every turn. There were cults that worshiped it, but their beliefs were insane even by Ruinous standards, and contradictory more often than not.

His attempt to gather enough psykers to force answers from the Warp had ended in catastrophe, and had been the catalyst for his excommunication from the Ordos. If not for the peril of leaving the threat of the Yellow King unanswered, he would have willingly surrendered to his peers for execution after that debacle. He still heard the screams, sometimes ...

He reached the door to Aemos' room, and forced himself back into the present. Even before crossing the threshold, Eisenhorn knew Aemos was dead. It wasn't the smell of blood, strong enough to pass through the door. Nor was it the fact that this particular alarm would only have triggered in circumstances the old man was unlikely to survive, or that he couldn't sense anyone alive in the room beyond with his psychic ability.

No, Eisenhorn knew his friend was dead because he was all too used to it happening. He recognized the sickening feeling in his guts, the pain tugging at the edges of his soul.

He took a deep breath to steel himself, and pushed the door open.

The room was covered in writing, from the papers and rolls of parchment to the furniture and even the wall. Aemos had started using ink, then once he had run out he had started carving the letters using the now-broken and discarded pens scattered on the floor. The most recent writing had been daubed on the walls with his own blood, the letters large and dripping.

Some part of Eisenhorn's mind pondered that it was a shame that a scholar of Uber's caliber had died writing a single word, over and over again : "no". So many years spent collecting data, all kinds of data, to feed his addiction, and in the end all of that wonderful knowledge had died with him. The books and notes Aemos had worked upon for years laid on the ground, their pages torn to shreds. A fragment laid next Eisenhorn's boot, and he picked it up carefully. He recognized its contents : they were from one of the clearest prophecies they had found about the Yellow King. It had been spoken directly to Eisenhorn, from a seer they had found deep in the bowels of an underhive ravaged by cult warfare. The seer in question had died immediately after speaking it.

"It will come,

The destroyer of hope,

The herald of despair.

It will come,

At light's end,

And end all that you hold dear.

It will come,

Unbound by death,

Untouched by life,

And you will know its name …"

The former Inquisitor finally turned his gaze to the body of one of his oldest friends. Uber Aemos laid on his back, his face a rictus of horror. He had torn out his eyes during his frenzy - the blood was already drying, so that must have happened early on, since the vitae on the walls was still fresh. Aemos' eyes had long since been replaced with augmetics, which laid on the ground a small distance away, broken as if they had been stomped on repeatedly. It hadn't been that horrific injury that had killed Aemos, though : there were gashes on his wrists, where he had used his quills to tear his veins open. Whether that had been to deliberately end his own life or because he needed more "ink" to write his message in, Eisenhorn would never know.

It wasn't the first time someone in Eisenhorn's employ had killed themselves while investigating the Yellow King. It wasn't even the first time they had ripped their own eyes out in the process. Before this, five other scholars in the rogue's employ had taken their own lives while investigating the entity. Knowledge of the Yellow King was not for the weak-willed, but Aemos had been at Eisenhorn's side since the beginning, and he had always been able to deal with the forbidden lore they had uncovered together. The data-savant must have found something – pieced together some terrible revelation that was finally more than he could bear.

He tooked more attentively at the body, and saw that Aemos had been holding something in his left hand during his frenzy – only the nails and fingers of the right one were broken. A piece of paper was barely visible, its corner protruding from the fist.

So tight was the dead man's grip that Eisenhorn had to break his fingers to loosen it. He carefully unfolded the piece of paper Aemos had clung to, and took the time to check all of his mental defenses were still in place before looking at what was written on it.

There were only eight words, written in ink with a trembling hand :

"IT IS NOT WHAT WE THINK IT IS"

For a long, long moment, Eisenhorn simply stared at the words, as if he could force them to make sense by strength of will alone. When that failed, he stood up and slowly tore the piece of paper apart, letting the fragments fall onto Aemos' corpse. He left the room with one last look back, and three servitors entered after he left. They would burn everything in the room, and then self-destruct, to make sure that no taint managed to latch onto them and escape the purge. The material within the chamber would have to be printed out again, from the warded cogitators where the original data was stored.

With Aemos dead, Eisenhorn needed someone to replace him, and continue the work of piecing together the clues gathered over decades of investigation. It was time to go to the Maze Undue, and see what kind of recruits the instructors there had to offer that met his requirements. Having to make an alliance with the heretics who ran the academy disgusted him, but it was a necessary evil. All the damage the Cognitae had ever inflicted upon the Imperium was nothing compared to what something like the Yellow King would do if it successfully manifested. Whether the instructors understood that, or merely went along with Eisenhorn's demands because they were terrified of him, was irrelevant.

Once again, Gregor Eisenhorn swore to himself, to his fallen friends, and to his God-Emperor, to whom his loyalty was still owed despite all that his former colleagues thought, that he would stop the Yellow King from entering reality.

No matter the cost.

AN : And here is the first part of the Halloween 2018 short stories. Until the 31st of October, I will be posting one such short story every day. Why ? Because I can, and because though I had only one such story (this one, in fact) planned at first, a question asked by a reader in the last chapter inspired me to write some more. Thanks you, Alpharius47. Writing these four stories has been a blast - and it's been remarkably relaxing. I wrote them all at once, jumping from one to the other until they were all completed. I wish I could do this more often, but now it's time to go back to full-length chapters.

I am currently working on finishing a short story I have had in the works for some time. It shouldn't be long until it's done.

I hope you enjoyed this little glimpse of what's to come after I have finished the Terran Crucible "book". According to my writing plans, Eisenhorn's fate will be next in the RH once that particular monster is done (the Terran Crucible is, according to my notes, going to be huge). I know a lot of you are very curious about the Yellow King, and while a part of me will be sad to deprive you of the joy of speculation by revealing the truth, I am quite confident you will like it - once you stop screaming, that is.

Well, that's all for today. See you tomorrow, for the next installement in the Halloween shorts : The Shadow over Hydra Cordatus !

Zahariel out.