Author's Note: Hello, all! This is a fun little fanfic I came up with, exploring what would happen if a Xenomorph infestation broke out in a Warhammer 40k hive city. I'm not expecting it to be very long, and I'll probably update it between chapters of False Imperium, though of course that project takes priority. Enjoy!

The patient was a tall, swarthy, unkempt man, about thirty, wearing a leather jacket with a faded Aquila on the back. Mazar Miklos accepted a stack of credits as payment, then directed him to sit on the exam table.

"What ails you?" Mazar asked, taking a rusty stethoscope and a thermometer from a cluttered desk drawer. His office was dim, one of the ceiling lights having burned out some time ago, and while he was by the desk he also switched on a small lamp so that he could at least read.

"Chest pain," the man said. "Can't breathe."

He spoke in an accent. Must have been a native of some distant hive, perhaps an offworlder. Mazar took clients of all sorts, and he didn't really care much about what they did or where they were from, as long as he got paid.

"Any other symptoms?"

The man shook his head. "None."

"I see. Do you smoke?"

"Quit lho-sticks five years ago."

There went one of the most obvious causes, but many other possibilities remained. Already he could tell the case was quite mild compared to the drug overdoses, infected injection sites, and occasional gunshot wounds he treated—all products of the lower hive in which he'd set up shop. This stood to be an easy day.

"Family history of asthma? Recent exposure to a respiratory irritant?"
"Don't think so, doc."

Mazar held the stethoscope to his chest, and listened. There was definitely something stopped up in there. The man's heart was beating faster than normal, his breaths were shallow and labored, and for a moment—it didn't last, he might have imagined it—he heard something squirming around.

He withdrew the stethoscope. Next came the thermometer, inserted orally, which read a slightly elevated body temperature but nothing too outrageous.

"Hard to say what your problem is. But I'll give you some full-strength Pyzarimine, should clear the airways up a bit. One hundred credits for a bottle."

"That's extortion."

"You won't find a better price elsewhere. And if you could go to an above-ground clinic, you wouldn't have come here in the first place."

Most practitioners kept detailed records. Mazar didn't, and that was attractive to a diverse clientele, evidently including this man.

The man scratched his scraggly beard. "Can I pay half now, half later?"

"I'd have no way of collecting."

"Fine." The man reached into a jacket pocket, and removed a stack of the colored chips that passed for currency on this world. Each bore the face of the Emperor or one of his nine mythical Angels.

"Very good. Let me run to my medicine closet real quick, and pick that up for you. Stay here."

Mazar turned and exited the room, leaving the door open behind him. There was a short hallway beyond. To the left were his squalid residential quarters, to the right was the room where he kept his drugs and surgical tools, locked securely to discourage local underhive druggies from breaking in. This was a rough neighborhood, but that was the price he paid for not having a medical license.

He had just dialed the lock combination when there was a loud crack from the other room. Like ribs breaking. The man screamed, and Mazar ran back over to see what was going on, arriving just in time to see his patient thrashing about on the exam table.

"What in the Emperor's name?" Mazar said. He stood in the doorway and watched the horror unfold.

Another crack. This time, blood spurted out from the man's chest in a fine mist, and he tumbled onto the floor. The screams and thrashing continued, and Mazar got the distinct impression that something was attempting to fight its way out of his client's body.

It was impossible to pry his eyes away—never in twenty years of medical practice had he seen anything like this. It was an obscene parody of birth, the eruption of some unknown and supremely violent parasite, which, presumably, had been gestating inside him for Emperor knew how long...

The ordeal of screaming and squirming ended when the parasite punched clear through the man's ribcage, spraying blood everywhere. He still twitched but was obviously dead. The creature, then… the creature rose from the fresh bloody hole it had made, a rounded head with a wide mouth and no eyes. It screeched. Its skin, if you could call it that, was pale, and its teeth were pointed like a dog's.

Mazar scrambled over towards his desk and unlocked the top drawer, where he knew he had a laspistol. He kept it around to defend himself against thieves, or the local gangs when they decided protection money wasn't good enough, but he had never expected he would need it for this.

The alien just sat there, regarding him. Its lack of eyes didn't seem to matter. While Mazar searched the drawer, crammed with lho-sticks and other vices, he glanced back at the corpse on the ground and the monster inhabiting its chest.

He found the pistol, picked it up. He never had been a good shot—he hadn't fired it in years—but in close quarters, against a stationary target, it wouldn't be too—

The creature jumped forward, using its long tail like a spring. Mazar caught a glimpse of stubby arms as it made a short hop through the air, but otherwise it was too fast to distinguish as anything other than a thick, pale serpent, and then it was by his feet, biting into his ankle.

Mazar screamed. The pain came upon him all at once, as teeth cut tendons, and even as he tried to shake it off it remained holding onto him. He fired a shot with the laspistol but only succeeded at blasting off the end of his foot.

He fell to the floor and hit his head against the desk on the way down. An attempt to get up again ended in failure when he slipped on the bloody wreckage of his foot. The creature wasn't biting his ankle anymore, he noticed, but that only meant it was somewhere else—hopefully somewhere far from him.

Mazar had no such luck. He heard slithering to his left, and saw the xenos abomination crawling slowly towards him, sizing him up.

"You little bastard," he said, spitting at it. He raised the laspistol.

It lunged, snapped at his hand. It took the pistol and three fingers with it, and then it was in front of his face, hissing, teeth bared.

That was the last thing he ever saw, because it went for his eyes next.

Author's Note: Thanks for reading! Next chapter should be a week or two out. Please let me know what you think in the reviews, and be sure to follow for more updates!