Warhammer 40,000: In Medias Res

===Prologue===
Author's Note: Special thanks to Stellar Elite for writing a small piece of this section.
The inside of the train car was a relatively quiet place, aside from the noise generated by the vehicle itself as it rumbled along a set of tracks suspended hundreds of meters above a featureless waste. Few of its passengers were yet awake, aside from the servitors that silently kept watch of the goings on within each of the many passenger cars, their mostly mechanical bodies requiring little if any rest. Martyn Rojas revelled in the peaceful quiet as he did what he did almost every day: gaze at the sky. As both a hive citizen and a manufactorum worker, the hour or so spent each day commuting between Spire Chylos and Manufactorum Mendrachis was the closest he ever got to the world outside the thick, bunker-like walls within the confines of which he lived out the vast majority of his existence. Sadly, there was little of interest to be found on the parched surface of Eneldor, which consisted largely of vast, barren wastes of reddish, iron-enriched soil and harsh, unfriendly-looking cliffs, gorges, and plateaus. These features were occasionally punctuated only by small, dilapidated settlements or by Skitarii outposts that looked just as unwelcoming as the nearly inhospitable terrain which surrounded them. It was this unforgiving environment that forced much of the population to spend their lives in a handful of monolithic manufactorum complexes and hive spires, for it was tacitly known that one must either be as tough as adamantium or a complete fool to dare venture into the dust-choked wastelands of Eneldor. But for as ugly and unappealing a planet as Eneldor was, Martyn could rarely help but find himself transfixed by its sky: a sprawling canvas of blue with swirling, wispy clouds and a rosy glow along the horizon.
As he gazed thoughtfully at the sky, longing to escape from his life of exhausting, menial work and into that blue sky and the starry expanse of space which laid beyond it, something unusual caught his eye. A small streak of white light, barely visible against the muted blue of the morning sky, disappearing just as quickly as it had flashed into existence. What in the Emperor's name?, Martyn thought. It must be the lack of sleep messing with my head. Indeed, Martyn rarely ever got much sleep, for the long hours he worked at the manufactorum left little time for much else, although never before had sleep deprivation caused his eyes to play tricks on him. But it was as likely an explanation as any for the bizarre sight.
It was only minutes later that the train screeched to a halt, the sound of metal scraping against metal ringing out as the brakes were engaged. "Destination reached: Manufactorum Mendrachis, entry gate four. Workers, prepare to unload," announced an artificial female voice over the train's voxspeakers. Martyn gathered up the few items he had with him; his work gloves and a small container of drinking water, and made his way out of the train car, glancing back for a moment at the servitor watching him and the other workers in ominous silence. Outside the train was an enormous atrium, its ceiling hanging at least half a kilometer overhead, with a massive cog-shaped window exposing the sky beyond. The atrium floor was roughly a one kilometer wide, and one and a half long, with a massive railway platform stretching across nearly the full width of the space, accommodating more than twenty sets of railroad tracks, with large walkways between each set of track. Lining the walls on either side of the platform were stone likenesses of tech priests, their gazes eternally transfixed upon the platform below and the workers that regularly occupied it. An enormous gate embossed with the sigil of the Priesthood of Mars stood at the far side of the atrium, beyond the end of the railway tracks, consisting of two massive adamantine blast doors each roughly two hundred and fifty meters wide and four hundred tall. The atrium was one of sixteen just like it, each designed to allow a portion of the manufactorum's vast workforce entry to the facility.
"Attention: work shift beginning in forty five minutes," warned the voice yet again, this time booming through the atrium's massive voxspeakers rather than the train's comparatively miniscule ones. "The Machine God favors those who are timely, and abhors he who is habitually tardy. Late workers will be forced to attend one week of remedial training as punishment. Praise the Omnissi-"
The sound of the final syllable was drowned out by an earsplitting explosion, as a massive object smashed through the atrium ceiling. Chunks of rockcrete rained down, crushing numerous innocents, while gigantic, jagged shards of glass maimed and impaled others. A slab of rockcrete several times larger than Martyn slammed into the ground less than two meters away from him, knocking him off his feet and nearly killing him. As Martyn righted himself he caught sight of the object which had crashed inside the atrium: an enormous chunk of coal-black rock, much unlike the rust-colored stone found in great abundance on Eneldor. Various ramshackle plates of metal and crude mechanical components covered the object, with what looked like a set of rocket engines cobbled out of scrap metal and other various refuse coughing plumes of thick black smoke into the air. But what was most concerning was not the object itself.
From the crater within which the object laid rose a number of green-skinned creatures. They were muscular and quite brutish in appearance, with pointed, dog-like ears and large teeth which protruded from their lower lip like tusks. There appeared to be no real uniformity in their garb, but it generally consisted of either soiled rags, primitive plate armor cobbled together from scraps of sheet metal, or some combination of the two. Though Martyn did not know much of the various xenos races which threatened mankind, he knew enough to know what these were.
They were Orks.
The hideous creatures brought to bear a terrifying assortment of rudimentary killing devices, from simple wood-and-steel axes to crude homemade firearms. With weapons in hand, they charged forth into the crowd of helpless workers, hacking, slashing, shooting, smashing, and stomping away with clear enthusiasm, howling with joyous delight at their prey's shrieks of anguish and cries of pain, leaving only mounds of mangled flesh, shattered bones, and pulpy gore in their wake. They tore their way through the atrium like a green-skinned tidal wave of carnage, bellowing the same guttural warcry again and again:
"WAAAAAAAAAAAAAAAAAAAAAAAAAAGH!"
Martyn found himself caught in the midst of a sea of confusion. He tried to push through the swathes of panicked people, staggering through the crowd while panting heavily. He found a clearing through the sea of people and broke into a sprint, running as fast as his legs could take up until the point he felt a sharp pain in his side. He was at least thankful that the Orks had less-than-substantial aiming skills, so this pain was from neither bullet nor blade. Martyn staggered his way outside, marginally more safe than the rest of the poor souls who were soon reduced to mincemeat by the greenskin onslaught, their crude and salvaged weapons proving to be horrifyingly effective. They looked as if they could barely work, yet they functioned better than most Imperial weapons. However, just when Martyn thought himself safe, a wave of agony erupted in his back as several projectiles penetrated his flesh near his shoulder blade. He fell to the ground, but attempted to stagger back onto his feet, only to slip on a slurry of dirt mixed with his own blood, his nose striking the pavement with a sickening crack. Martyn, his physical faculties exhausted, slipped into unconsciousness, just as the pain from his newly-broken nose began to wash over him.
As Martyn silently succumbed to his injuries, another Orkish vessel descended into the atrium through the crumbling ceiling, slowing to a stagnant hover just a short ways from the center of the gore-spattered railway platform. From the ship's hold dropped a truly massive Ork, clad in a suit of primitive power armor, driven by a diesel piston engine which belched puffs of smoke angrily about.
"Ya see, boyz!?," the beast roared. "Dis iz wot 'appenz ta gitz 'oo fink dey'z ken muck about in Bad Moonz space! Dis iz wot 'appenz ta gitz 'oo mess wiv Boss Roktoof! Now letz ged in dere 'n show deez 'umies 'n dere stoopid 'Em-purr-oar' git 'oo'z da biggest 'n da 'ardest!"
==Chapter One==
An almost indescribable sort of restlessness gripped the crew of the Fury Reborn as it emerged from the perilous tides of Immaterium. One might've called it anxiety if they didn't know better, but the Space Marines of the Doom Eagles chapter had long abandoned the sort of fears which were implicit to the term. More accurately it was a strange eagerness: eagerness to meet their enemy in combat, coupled with a feeling of apprehension which came naturally with the uncertainties of an impending battle. Even a seasoned Battle-Brother such as Veteran Sergeant Egon Talorus was not immune to such a feeling, although roughly three centuries of experience had taught him how to control and channel it. For all of the uneasiness which fluttered about in his chest, he maintained about him an icy composure and a stern confidence. After all, doubt was a luxury that the Sons of Aquila could hardly afford to possess.
The bridge of the Fury Reborn offered no reprieve from the tension which gripped the ship. Although it seemed relatively quiet and calm at a glance, the fact that not one of the chapter serfs looked up from what they were doing when Egon entered the room told him plenty. However, the tension here was borne of something entirely different than in the rest of the ship: Captain Hectorius, Egon's commanding officer and Master of the Doom Eagles Fleet, stood at the center of the bridge, carefully scrutinizing the command crew's every action. Hectorius ran a far tighter ship than any Fleet Master in the chapter's recent memory, and as such there was little room for error on his bridge.
"Brother-Captain," Egon started, only to bite his tongue upon realizing that the Captain had already begun speaking to someone over the ship's holographic vox projector, and instead began to walk silently over to Hectorius' side. As Egon drew nearer he could tell that the individual on the other end of the vox was, unsurprisingly, a fellow Astartes, but Egon couldn't help be sense that there was something curious about the Marine's armor. Almost as though he recognized the Marine, but couldn't quite place who they were. But once Egon came close enough to make out the Marine's heraldry, it all made sense. His armor was painted in a two-toned scheme of red, with a subtle silver trim, the heraldry of the Aetherian Warriors chapter.
"Fulvio Caro?"
In his disbelief, Egon had let the name slip from between his lips, interrupting his Captain's conversation. Both the Captain and the Aetherian Warrior's holographic avatar turned to face his, Hectorius' face quickly morphing into a particularly sour expression. "Oh, Egon Talorus, isn't it?," the Aetherian Warrior mused. "I see you remain alive and well. I hope you aren't still upset about what occurred during our last encounter. It was simply a matter of business, after all," he continued, confirming his identity. A beastly rage welled within Egon upon hearing Fulvio's words, but Egon managed to remain in control.
"With all due respect, Captain Caro, I wouldn't consider leaving an entire Company of your own Brothers for dead and causing the death of another Chapter's Captain to be 'simply a matter of business'." Egon's tone was cold as ice.
"So you are still upset. What a shame," Fulvio remarked, not so much with disappointment as with distaste. Although Egon could not see Fulvio's face, he still seemed as though he was about to say more, but Hectorius cut in before he could do so. "Watch your tone, Sergeant. I will not allow grudges to interfere with the enactment of the Emperor's will as long as I am in command of this Company."
Unbelievable. Captain Diominus Feldon had been the one to name Hectorius as his successor, and here he was, spitting upon his predecessor's grave by fraternizing with the very individual whom had been deemed responsible for Feldon's death. But in many ways, Egon couldn't help but admit to himself that the Captain was still right. Both they and Fulvio were here to carry out the Emperor's divine will, and that was all that truly mattered. At least for the moment.
"Very well, Captain," Egon apologized. He turned to Fulvio's avatar. "Forgive me for my outburst, Captain Caro. It was most unbecoming of me."
"You are excused, Sergeant," Fulvio replied, although his tone didn't seem particularly sincere to Egon. "Captain Hectorius, I shall have your revised battle plans distributed to my men within the hour. Sanguinius bless us." Fulvio's holographic avatar flickered and faded from sight.
Hectorius looked over once again to Egon, the irritated scowl still not having left the Captain's face. "I expected better from you, Sergeant. I know just as well as you what Captain Caro is guilty of, but his Chapter declared his actions to have been just. There's nothing we can do to change that now." Egon nodded understandingly. "But that's beside the point, regardless. We have a job to do here, Egon, and we're going to get it done even if we have to work with the foulest scum in the Imperium to do so." He paused for a moment, his face returning once more to its typical, neutral expression. "Now what have you to report, Sergeant?"
"I have gathered my squad, Tactical Squad Boracius, and Assault Squad Aliphonsius in Deployment Hangar Sigmatum. Just as you requested, Captain," Egon informed the Captain, to which he gave a approving nod. "Excellent. Our battle plans underwent some last minute changes, at the behest of the Dark Angels' Company Master, Orias." The Captain's expression became momentarily sour at the mention of the Dark Angels, something which Egon found perplexing.
"Is something wrong, Captain?"
Hectorius let out a long, clearly exasperated sigh. "Come along, Sergeant," he said, motioning for Egon to follow him as he made for the door. Egon complied, of course, albeit rather put off by the Captain's dodging of his question. As the door to the bridge closed behind them, however, Hectorius stopped abruptly. "Let me be honest with you, Sergeant." Egon turned, having not realized that Hectorius was no longer walking directly beside him. "I'm not sure if I trust the Dark Angels."
The two Marines looked at each other in silence for almost a full minute, neither one quite sure what to say next. "You trust Captain Caro," Egon thought aloud, finally breaking the silence, trying to make sense of his Captain's words. "But you don't trust the Dark Angels? Not only that, but a company of Dark Angels who fought and bled beside us on Mendravium?"
"Captain Caro is a bad seed within an otherwise fine and honorable chapter. The Dark Angels, however..." The Captain's voice trailed off.
"Captain, are you doubting the reputation of a First Founding Chapter? The immediate kinship of a Primarch?"
"You're a good man, Sergeant, no doubt, but you trust too easily. No one is above suspicion, Egon; not ever. And as for me personally, something about the Dark Angels rubs me the wrong way. It's almost as though they're hiding something."
Hectorius pushed past Egon, climbing onto a nearby service gravlift. Egon remained unmoving, however, still trying to wrap his mind around the Captain's bold accusations.
"Coming, Sergeant?," Hectorius asked. "We're to deploy within the next two hours, and we still have much to do. This little chat has already begun to eat into time that we quite frankly don't have."
Egon nodded, his composure and sense of purpose returning to him at once, and he stepped onto the gravlift as well. But within the back of his mind Egon knew that his Captain's worries were a bad omen. Should he find himself forced to choose between defending the honor of his Captain or defending the honor of the Dark Angels, Egon was not entirely sure which side would be the right one to take. And doubt was a luxury that Egon could ill afford.