Chaos are Space Marines turned to and corrupted by the Ruinous Powers of Chaos. They are the arch-enemy of the Imperium of Manand the evil counterpart of the Adeptus Astartes.
Visually, the Chaos Space Marines are somewhat over-the-top evil; occult symbols, horns and other sharp armor protuberances, wickedly shaped weaponry, skulls and the like are common, but this actually helps to both call upon the power of the Warp and demoralize the Imperials. Orks sometimes refer to them as the "spiky boyz" and like to loot the "spiky bitz".
During the Great Crusade, approximately 10,000 years before the Dawn of War series, the Imperium was at the apex of its power, reclaiming colonies lost during the Age of Strife and expanding beyond, crushing all opposition. Some of their mighty Space Marines, however, showed signs of instability, the Astartes inheriting the quirks of their progenitor Primarchs. One of these problematic Legions were the Word Bearers.
The Word Bearers Legion, guided by Primarch Lorgar, were unmatched in their zeal for the Emperor, to the point of venerating him as a god and forcibly converting all conquered worlds to this belief; it was actually the Word Bearers who first conceived Space Marine Chaplains. The Emperor, trying to create a secular and rational galactic nation, became increasingly frustrated by this, and finally had to step in when the Word Bearers started persecuting and massacring civilians who refused to accept the Imperial Cult. A cathedral city on Khur, a model world of the Word Bearers, was destroyed by the Ultramarines and Lorgar with his entire Legion ordered to assemble in the ruins. The Word Bearers were harshly rebuked and humiliated, leaving Lorgar stunned and melancholy.
Lorgar came to believe the Emperor was not a god, but true gods did exist somewhere. He researched the old religion of his home world Colchis and consulted Magnus the Red. He perceived a common origin in all of the ancient human religions and launched "the Pilgrimage", an expedition to find this origin in "the place where gods and mortals meet". The Word Bearers were split to spearhead the Great Crusade on all fronts in search for this origin. The search finally led Lorgar himself to Cadia, where a native guided him to the Eye of Terror, the discovery of the Chaos Gods, and eventually the corruption of the Word Bearers.
The Word Bearers started undermining the Astartes from within and converting Primarchs to their cause. They orchestrated the mortal wounding of Warmaster Horus, performed with a "Primarch-killer" weapon stolen from an advanced human-alien civilization, and persuaded the Luna Wolves to employ tribal sorcery – later revealed to be Chaotic in origin – to revive him, when Imperial medicine could not. Making use of the Warmaster's illness and feelings of guilt and anxiety over the actions of the Imperium, Horus was turned and the betrayal spread. Several other Primarchs were converted by Horus and Lorgar, and the plot culminated in the massacres on Isstvan III and Isstvan V, where Loyalist troops were deployed on the surface by orders from Horus, then bombed from orbit and assaulted by traitor forces. This began a galaxy-wide civil war known as the Horus Heresy.
At the apex of the Imperium's power, at least nine of the twenty original Legiones Astartes turned to Chaos and rebelled, pulling large amounts of the Imperial Army and even the Adeptus Mechanicus with them. Led by Horus, the first recovered Primarch and the adopted son and right hand of the Emperor, they almost destroyed the whole Imperium. A more terrible war has never been known by the galaxy; even the most terrible battles of the 41st millennium can only begin to aspire to sheer savagery of the myriad skirmishes and engagements that erupted during the galaxy-rending civil war.
The Horus Heresy stopped only when the Emperor himself managed to slay Horus during a nearly decisive siege of Terra (Earth). The armies of Chaos collapsed and escaped, pursued by enraged Loyalist Legions, finally retreating to the Eye of Terror and other Warp Storms. There they now reside, occasionally attacking Imperial territory. Because of weird passage of time within the Eye, some of the present-day Chaos Marines are the actual survivors of the Horus Heresy and have actually just participated in it a minute ago; others (sometimes even whole Chapters) have turned to Chaos later, swelling their numbers.
Retaining the tremendous physical and mental advantages of their status as Space Marines, combined with the gifts of the Chaos Gods, the Traitor Legions are, individually at least, far more capable combatants than even their Loyalist brothers. Due to the immortality granted to them and the skewed perception of time within the Eye of Terror, these former Space Marines maintain a massive percentage of their number as actual survivors of the Horus Heresy itself. Thus, they are highly experienced warriors, and well-aware of Imperial tactics. As it was they, who in the first place, contributed to them.
However, the Chaos Legions are highly divided. Due to their service to such capricious Gods, warbands frequently infight amongst themselves in order to prove themselves worthy in the eyes of their masters. It is perhaps for this reason alone, that the Imperium and the galaxy itself continues to evade the full brunt of the anger of the Traitor Legions. These confrontations are in part motivated by religion, as each of the Dark Gods are diametrically opposed to one another. The opposition stems from the conflict between whatever emotion of concept the Gods personify. Khorne, being a warrior god, a being of honor and strength sees the effluence and honorless indulgence of Slaanesh as sickening, much like the desperation and succumbing to fate personified by Nurgle or the treasonous sorcery of Tzeentch. Thus breeding the enmity between the gods. This hatred is carried over to their followers, who reciprocate the hatred between their patrons in the physical world through combat. The constant raiding is also for supplies; geneseed, resources and slaves. The Black Legion attempt to counter this by worshipping "Chaos Unidivided", but are still plagued by infighting.
But despite that, the Chaos Legions are far more driven by their eternal vendetta against the Imperium of Man. A conflict they have dubbed 'the eternal war'. As such, the terrible forces of Chaos frequently raid out against the Imperium. Every last one of these incursions are often beaten back by a terrible cost to the Imperium. These invasions range from small warbands raiding out amongst the Imperium's threshold worlds, right into the apocalyptic Black Crusades led by the heir of Horus, Abaddon the Despoiler.
The Arms and Armors of ChaosEdit
The Chaos Space Marines are incapable of benefiting from the technological advances the Imperium has made since the Horus Heresy. What litte there is. More importantly, they are mostly without the proper equipment to manufacture more weaponry, though occasionally, the Chaos Legions capture Forge Worlds and turn them to Chaos to provision their forces. The Traitor Marines compensate for their aging technology with the power of Chaos.
The daemonic energies of the warp enchant and strengthen their armaments and armors. The so-called Dark Mechanicus work tirelessly to forge unholy warmachines such as the Defiler. The Chaos Gods themselves bless the artifact weaponry of the Chaos Marines with new, daemonic additions to their armory. Most noteworthy, the Chaos Gods, as a sign of favor send down their greatest gifts to their most 'spiritually pure' Chaos Lords; the terrifying Daemon Weapons. Weapons that hold within them the terrible spirits of raging daemons, malevolent entities who's terrible insanity can only be controlled by only the most powerful and determined Chaos Lords. To wield a Daemon Weapon is a mixed blessing, though such a weapon is indeed amongst the greatest in all the universe, capable of slaying the greatest foes easily and worthy of the mighty Chaos Lords, it is also true that the wielder is locked in an battle of wills against the daemon within the warp-forged steel. Only the most terrifying and potent Chaos Warriors can bear such weapons in battle and fewer still can retain any measure of fleeting sanity or control.
With these terrible weapons, the Chaos Legions have firmly placed themselves as one of the most potent fighting forces in the galaxy. More than capable of facing their hated enemy, the Imperium, and matching them blow for blow.
The Black CrusadesEdit
Following the devastating events of the Horus Heresy the Imperium began a campaign to cast out all traitors who had sided with Chaos and drove them into the warp storm known as the Eye of Terror. There, the followers of Chaos began to fight among each other for domination and territory and their vast armies eventually fractured.
Even so, the threat the exiles posed was far from gone. To this day they seek to overthrow the Imperium, launching separate raids and invasions against it. Once or twice within a millennium however, an exceptional Chaos Champion rises who is strong enough to bring his fellow warlords and their hosts under his sway. When this happens ancient rivalries are set aside and uneasy alliances are forged, clearing the way for what is called a Black Crusade.
The forces and fleets that gather for a Black Crusade are made up of all types of Chaos servants: the multitudinous hordes of the Lost and the Damned, ancient and towering Chaos Titans, the bizarre warmachines of the Dark Mechanicum and the Daemons of the Warp. Leading them into the realm of man are the vengeful warbands of the Chaos Space Marines.
When the crusade is launched, whole worlds fall prey to the rampaging hordes and the Dark Gods themselves divert their attention to the material realm, delighting in the sacrifices made in their names. Still, the nature of Chaos is fickle and unless it is repelled by the defenders, the crusade is bound to splinter into separate hosts and warbands who pursue their own ambition.
Lord Abaddon himself has led 13 Crusades against the Imperium, though ultimately beaten back at every turn, the Crusades have dealt mortal blows to the Imperium, and the High Lords of Terra live in fear of the day Abaddon will finally unite the Hordes of Chaos and play out the last acts of treachery Horus began ten thousand years ago.
Abaddon alone is not the only Chaos Lord great enough to conjure such an army against the followers of the "Dead Emperor". Other Chaos Lords and Daemon Princes have also carried such a banner against the Imperium. With dark success. Such an example is of the Khornate Daemon Prince Doombreed, most favored of Khorne, who led a crusade against the Adeptus Astartes, wiping out two entire chapters, the Warhawks and the Venerators. Another is of the Blackstar Crusade, led by the Champion of Khorne, Lord Ekrak, which culminated in his ascension to Daemonhood.
- Alpha Legion
- World Eaters, dedicated to Khorne
- Word Bearers
- Black Legion, previously known as "Luna Wolves" and "Sons of Horus"