Chaos Space Marines army rules, detachment abilities, stratagems and lore for Warhammer 40k, with links to the full unit datasheet table.
Chaos Space Marines, also sometimes called Traitor Marines, Renegade Marines, or Heretic Astartes, are former Space Marines of the Imperium of Man who have chosen to abandon the service of the Emperor of Mankind and dedicate themselves to Chaos to achieve their own ends.
Such corrupt Astartes usually belong to one of the nine original Traitor Legions that betrayed the Emperor during the ancient civil war called the Horus Heresy more than 10,000 standard years ago, while others come from Space Marine Chapters created long after the Heresy ended that have turned Renegade. Chaos can corrupt Astartes of any time and place just as its siren call leads many lesser men and women to their damnation.
During the Horus Heresy, the terrible Imperial civil war that pitted the battle-brothers of the 18 known Space Marine Legions against one another, there were two factions. These were the Loyalist Space Marines who continued to serve the Imperium and the Emperor of Mankind and the Chaos Space Marines of the Traitor Legions who betrayed the Emperor and pledged their souls to the service of the four Ruinous Powers of Chaos.
Some Traitor Marines pledged their service to all four of the Dark Gods, a malevolent force known as Chaos Undivided, whilst others preferred to dedicate themselves to the worship of only one of the Ruinous Powers. The Traitor Legions were led by the Warmaster Horus, once a primarch of the Imperium and the Emperor's most trusted friend, son, and adviser before he was corrupted by the promises and lies of the Dark Gods and his own inner flaws and ambition.
The Traitor Legions were the most powerful component of the forces of Chaos which fought during the Heresy, which also included the myriad Daemons of the Warp, Human Traitors from the Imperial Army, the potent infantry and combat walker forces of the Dark Mechanicum and Chaos Cultists drawn from across the galaxy.
The flesh and power armour of Chaos Space Marines often warps and twists into new, darker and inhuman forms under the influence of the Warp energies they are exposed to as their shapes morph to embody the corrupted Astartes' new allegiance.
Chaos Space Marines fight for everything they were once forbidden to indulge in as the ascetic servants of the Emperor and the selfless guardians of Mankind. Pleasure, wealth, mayhem, but above all else, the power to rule their fellow Humans in the name of the Chaos Gods is the driving ambition and goal of every Chaos Space Marine.
All Heretic Astartes are ultimately united by this sheer hunger for power. At first, this desire is focused towards specific goals, but as time passes, it becomes a bone-deep obsession. Though the Dark Gods are given to rewarding their mortal followers for acts of carnage that further their divine cause, the gifts they bestow upon their favoured are fickle indeed.
A particularly extravagant slaughter might be rewarded with a blood-red aura that invigorates the supplicant, but it is just as likely the champion will find his arms being reshaped as axes of bone, or that he has the face of a slavering hound.
Eventually, the Chaos Space Marine seeks immortality, to ascend to such lofty heights of favour that he is remade as a Daemon Prince. But for every successful aspirant there are hundreds of failures, mutated beyond recognition into mewling abominations called Chaos Spawn.
The Traitor Legions of the Chaos Space Marines represent 9 of the 20 original First Founding Legions of Space Marines who were created by the Emperor of Mankind from the genomes of his 20 primarchs in the late 30th Millennium to fight the Great Crusade that forged the Imperium of Man.
At this time Horus, the Warmaster of the Imperial forces and primarch of the XVIth Legion, the Luna Wolves, (which the Emperor allowed him to rename the "Sons of Horus" in his honour before the onset of the Horus Heresy to demonstrate his status as first-among-equals among the other primarchs), was corrupted by Chaos. The Warmaster then instigated the galaxy-wide Imperial civil war known as the Horus Heresy in his determination to replace the rule of the Emperor with his own.
After the death of Horus at the hands of the Emperor aboard his flagship, the Vengeful Spirit, during the Battle of Terra that saw the conclusion of the Horus Heresy, the remnants of the nine Traitor Legions fled, along with the other Traitor Imperial forces that now served Chaos, into an area of the galaxy where the Warp bled into realspace, creating the permanent Warp Storm known as the Eye of Terror.
Due to the nature of Chaos, and the temporal instability of the Warp, many of the very same Chaos Space Marines who revolted against the Emperor more than 10 millennia ago continue to fight against the Imperium today, having effectively been granted a tortured immortality by the will of the Ruinous Powers.
The Traitor Legions have kept their old names, with the exception of the Sons of Horus who were renamed the "Black Legion" by their new leader, Abaddon the Despoiler, once Horus' chief lieutenant and the first captain of the Luna Wolves before he followed Horus into damnation. Besides Horus, two other Traitor primarchs were killed during or shortly after the Heresy (Alpharius of the Alpha Legion and Konrad Curze of the Night Lords).
The six surviving Traitor primarchs have since been transformed into Daemon Princes by the Chaos Gods. These Daemon Primarchs rarely took part in the affairs of their Legions before the birth of the Great Rift. Four of the Traitor Legions have pledged a singular loyalty to one of the great Chaos Gods, while the others serve the interests of Chaos as a whole in the form of Chaos Undivided.
Due to the nature of Chaos and those who choose to serve it, not long after the end of the Heresy the Traitor Legions, save for the Word Bearers, largely stopped operating as unified military organisations and instead devolved into a series of separate and often competing smaller units called "warbands." The Traitor Marines who command these warbands, all potent Chaos Champions, seek their own personal glorification and the eventual opportunity to become Daemon Princes in their own right by earning victories in the cause of Chaos.
Due to the fractious nature of the Dark Gods, the warbands in service to a particular Ruinous Power often view other Traitor Marine warbands who serve its patron's rival deity as even more appropriate targets for their wrath than the servants of the Emperor. With such an attitude prevailing among the corrupted Astartes, it has often proven impossible for the Traitor Legions to present a united front against the Imperium since the death of Horus, which is one reason why they have never enjoyed a similar series of military successes over the past ten millennia.
Lore excerpt from Warhammer 40k Wiki on Fandom, available under CC BY-SA 3.0.
58 Chaos Space Marines datasheets on the current roster, each with its points, model statistics, keywords and abilities.
54 Chaos Space Marines datasheets that are no longer part of the current army roster. They are kept for reference and for players whose collections still contain the models.