Realm Guard and Mercenaries

The million worlds of the Imperium have been fractured between the thousand warring realms that now rule humanity, undoing all the Emperor had accomplished in the Great Crusade. Ironically, in this fractured state the galaxy is closer to what it truly is: a collection of diverse and terrible worlds with ecologies and cultures so utterly different from one another that they are irreconcilable. However, this lack of uniformity is the strength of an interstellar empire, as all manner of men and women are available to serve the Legiones Astartes as auxiliaries and vassals. From the hottest worlds and the coldest corners of the galaxy come the Realm Guard, the Knight Houses, and the mercenaries of Segmentum Tempestus.

Realm Guard

The space marines are the greatest weapon of their realm, but humans are their most numerous. The Realm Guard are common men and women called upon by their masters to fight in faraway worlds, never to see home again. Each guardsman is given what their world can afford; at minimum, it is the primitive weapons of a feral world, and the logical limit is in superheavy tanks and advanced armament from a forge world. Regardless of kit they are not expected to live long, for in a universe of supermen and devious creatures normal humans are of little worth as soldiers. Rather, their strength is sheer numbers, exceeding all the space marine legions combined a thousandfold. Without the Realm Guard, the worlds of the galaxy would fall to xeno forces who exploit the small numbers of the Astartes, and even one decisive battle between legions could decide the fate of an entire realm.

Anthrax Chem Guard

Far within the reaches of the Dark Imperium lies a poisoned bastion world of insects and toxins. A deadly forest covers the planet in a coat of noxious gas, its roots and spores reaching deep into the ground and across the land spreading its poisons. Only the Chem-Bastions of Anthrax, manufactor-fortresses, can protect the Anthraxians from the forest's blight. The cramped Chem-Bastions provide insufficient sustenance for its population, and little work is available for the massive swathes of homeless. The only way to escape from the confines and destitution of Anthrax is to join the Chem Guard, and fight the Warmaster's enemies in the Galaxy.

Every year the marshals of Anthrax hold a lottery for the privilege to join the Chem Guard; for a small price a citizen may have a chance of finally leaving the dangers of turning gears and deadly gas, but even then only slim. However, the recruits quickly find themselves in a different kind of peril. The Chem Guard is so named for its affinity for deadly life-eating weaponry-chemical weapons, biological agents, and rad weapons of unparalleled power. The Chem Guard's method of warfare is a slow and violent one: surround the enemy, shell and gas them, spread plague and radfire within their walls and cities, and grind them to nothing. The battle against Anthrax troops is one of attrition and willpower, but few on either side of the line have the will to survive Anthrax's poisons. If not for their masks the Chem Guard would die as quickly as the enemy, but even with protection from the gas and the plague they are still susceptible to the lasbolts and the ordnance of the enemy, and thus the life of a Chem Guard legion is short and taxing.

Corps 0

The concerns of the Dark Imperium lie not in the preservation of its people, but the destruction of the galaxy. Aboard a secret space station in deep space are a myriad of dark projects conducted by the Dark Mechanicus, among them the production of suicide troops pumped full of combat drugs and low-quality bionics. Corps 0 is their designation, an impersonal designation that highlights their lack of humanity. Placed in cryosleep, a regiment of Corps 0 is shipped off in a transport to their first and last battle, where they shall achieve their one mission and perish.

Corps 0 burns quickly like a raging inferno, destroying everything in its path before succumbing to wounds or their own enhancements, both chemical and cybernetic. The Corps 0 regiment is given its target - a hill, a fortress, a titan or baneblade company - and unleashed on the battlefield. Zero Troopers rush their enemy in a suicidal charge, ignoring the pain of gunfire and flying shrapnel, and meet the enemy in close quarters. With reflexes temporarily enhanced they tear opponents limb from limb until either the enemy or the enhancements kill them, and without any concern for their own well-being they tackle vehicles and equipment with explosives strapped to them. The soldiers of Corps 0 were not meant to live; if their own cybernetics don't tear themselves from the flesh, or if their combat stims don't cause catastrophic organ shutdown, then the enemy would certainly kill them. However, even if the attack fails, it is all but certain that Corps 0 had inflicted enough damage for a follow-up attack to finish the job.

Karadon Cold Ones

Karadon is a world of ice and fire. Its seasons are at the mercy of the planet's tectonic instability and the dangerous asteroid ring too close for safety. When the world is stable and the skies are clear, the lands freeze and the oceans hide under thick ice. When the Ring of Fire around the equator erupts violently, it pumps gases into the atmosphere that trap the sun's heat and scorches the surface, plummeting Karadon into darkness and fire. But woe truly comes when the rare asteroid impacts the planet, shattering it and awakening ancient creatures from deep within the crust. To compete with the machinations of the universe, the Saurians of Karadon have evolved adaptations specific to each event, the ecosystem alternating with the cycle of ice and fire. In the times of fire, cold-blooded predators emerge from their slumber, smelling the sulfur and blood that choke the atmosphere. In the times of ice the cold-blooded Saurians hibernate and make way for the hot-blooded ones, who scour the land for prey.

The people of Karadon too have adapted to the cycle. They are a primitive collection of tribes, too backwards to be called civilized, whose culture is based on the Saurians. They hunt them, eat them, capture them, tame them, and ride them. When the Undying Scions come to Karadon and the Karadoni give their pound of flesh, they bring their beasts with them. Thus the Karadon Cold Ones are two regiments: The Cold Years who master the tundra and ice fields, and the Hot Years whose Saurians excel in the heat. Their pets are all manner of beast, from the miniscule petaraptors to the colossal gigarexes, their teeth all sharp and deadly.

Argon Silverbacks and Argon Apemen

Argon is a stormy ocean world, with only one large island that houses a massive prison. This is the Argon Correctional Facility, the home of countless inmates and the charge of the most brutal prison guards in the Jade Empire. The scum of the galaxy are in a constant conflict with their jailers, a never-ending battle between the criminals craving freedom and the guards who must violently repress their desire for such. It is prime ground for Chaos influence and infiltration, and the jailers must be ever-vigilant for the spread of heresy within the facility, and would not bat an eye if they had to purge the prison as they have many times before.

The inhospitable conditions are the perfect environment to raise tough and violent warriors, but it also creates violent sociopaths who have a disdain for authority. The Sky Serpents come by to sweep up penal soldiers from the planet, sending the weaponized criminals called the Argon Apemen to battle with explosives where one of their kidneys should be. They are a rabble of unlucky but undeserving souls, convicts trudged up from many gangs and cell blocks, an assortment of ogryns and ratlings mixed with less-than-pure aliens, that would be as prone to fighting themselves and their allies as the enemy if not for the scars on their bellies reminding them of their duties.

However, the Apemen alone are not sufficient for the war effort. From the jailers of Argon are drawn the elite troops, the Apemen's alpha so to speak. The Argon Silverbacks bring with them the tools of their trade: shotguns, lasguns, carapace armor, riot shields, repressor transports, and brutal techniques and inventions for controlling unruly cons. Behind a thick line of cybernetically-controlled bullgryns and rhinos they hide as they advance down streets, moving from building to building to clear them of the enemy.

Brimstone Fire-Eaters

The planet Brimstone is so rightly named, for it is an unstable world that mines the sulfur spewed from volcanoes and the promethium pouring from the toxic oceans. Its people are hearty and spiritual, but deeply disturbed at their hearts. They spend too much time in the foundries and mines of Brimstone, and over their lives they inhale fumes that degrade their minds and bodies. Life on Brimstone is one of hard labor and a slow descent to madness, and so many are happy to leave once the Storm Hammers come to the world seeking warm bodies for the eternal war against Chaos. With them the Brimstone Fire-Eaters bring their heavy hazmat suits that protect from fire and chemicals, and their handy reserves of holy promethium to cleanse the galaxy in flame.

The tools of the Fire-Eaters are fire and hate. Flamers, hellhounds, incendiaries; the stuff that cleans the soul and purifies the land. Pyromania is the Fire-Eaters' forte, and they live to burn the enemy to pure ash. They are the feared shock troops who sweep buildings with holy promethium and walk through the flames untouched. They are the shock troops who break the heretics, the flame that incinerate ork spores before they can take root, the light that shows the way to righteousness.