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The forces of Chaos in Warhammer 40k are not a monolithic army — they are a fractured collection of Traitor Legions, renegade chapters, and independent warbands, each with their own history, allegiance, and reason for turning against the Imperium. From the nine original Traitor Legions who sided with Horus during the Heresy to renegade Space Marine chapters who fell to corruption millennia later, the galaxy is filled with warriors who serve the Dark Gods.
This is a guide to the major Chaos Space Marine warbands in Warhammer 40k. We cover the nine Traitor Legions, the most significant renegade chapters, and notable independent warbands. For each, we cover their origin, allegiance, notable leaders and what makes them distinct. We have stuck to warbands that appear in Games Workshop’s published material, and kept the descriptions short where the official background is thin.
The Nine Traitor Legions
These are the original Space Marine Legions that betrayed the Emperor during the Horus Heresy in the 31st Millennium. Each was led by a Primarch who fell to Chaos, and each has evolved in its own way over ten thousand years of war.
1. Black Legion (formerly Luna Wolves / Sons of Horus)
Primarch: Horus Lupercal (deceased) | Current Leader: Abaddon the Despoiler | Allegiance: Chaos Undivided | Colours: Black with gold trim
The Black Legion is the largest and most powerful Chaos Space Marine force in the galaxy. Originally the Luna Wolves — Horus’s own Legion — they were renamed the Sons of Horus during the Heresy. After Horus’s death, the Legion fractured until Abaddon reformed them as the Black Legion, painting their armour black to symbolize their shame and their new purpose. Abaddon leads them in the Long War against the Imperium, and his 13th Black Crusade destroyed Cadia and tore the galaxy in half with the Great Rift. The Black Legion accepts warriors from any background, making them the most diverse and numerous Chaos force. They are the default Chaos Space Marine faction and represent Chaos Undivided — serving all four gods without being beholden to any single one.
2. World Eaters
Primarch: Angron (Daemon Primarch) | Allegiance: Khorne | Colours: White and blue (pre-Heresy), red and brass (current)
The World Eaters are the berzerker legion of Khorne, the Blood God. Their Primarch Angron was implanted with the Butcher’s Nails — cortical implants that amplify rage while suppressing all other emotions — and he eventually forced these devices on his entire Legion. The World Eaters live for close combat and care nothing for strategy, tactics, or even self-preservation. They fight in a blood-mad frenzy, screaming Khorne’s name as they butcher everything in reach, including each other. They have had their own standalone Codex since 10th Edition, reflecting their importance as Khorne’s chosen legion. Their most famous champion is Khârn the Betrayer, who earned his name by attacking his own allies during the Siege of Skalathrax.
3. Thousand Sons
Primarch: Magnus the Red (Daemon Primarch) | Allegiance: Tzeentch | Colours: Metallic blue and gold
The Thousand Sons are the sorcerous legion of Tzeentch, the Changer of Ways. Once a legion of scholar-warriors devoted to psychic mastery, they were censured at the Council of Nikaea and ultimately destroyed by the Space Wolves during the Burning of Prospero. In a desperate attempt to save his remaining brothers from the flesh-change mutation, the sorcerer Ahriman cast the Rubric of Ahriman — a spell that stabilized the mutations but turned every marine without psychic ability into an empty suit of armour filled with dust. Now the Thousand Sons are an army of dust automatons led by powerful sorcerers, all serving the scheming plans of Magnus the Red. They have their own standalone Codex and play as a sorcery-focused army built around Rubric Marines and their sorcerer leaders.
4. Death Guard
Primarch: Mortarion (Daemon Primarch) | Allegiance: Nurgle | Colours: Pale green, corroded metal
The Death Guard are the plague legion of Nurgle, the God of Decay. During the Horus Heresy, the entire Legion was trapped in the Warp and subjected to Nurgle’s Destroyer Plague by their First Captain, Typhus. Mortarion was forced to pledge his Legion to Nurgle to end their suffering. Now the Death Guard are walking corpses filled with disease and corruption, yet supernaturally resilient — they feel no pain and cannot be killed by conventional means. They spread Nurgle’s blessings wherever they march, turning worlds into plague-ridden wastelands. With their own Codex, they play as an extremely durable, slow-advancing army that grinds opponents down through attrition and mortal wounds.
5. Emperor’s Children
Primarch: Fulgrim (Daemon Primarch) | Allegiance: Slaanesh | Colours: Purple and gold, often with excessive ornamentation
The Emperor’s Children are the hedonist legion of Slaanesh, the Dark Prince of Excess. Once the most disciplined and perfectionist of all Legions — so honoured they were permitted to bear the Emperor’s own heraldry — their pursuit of perfection led them to seek sensation beyond mortal limits. They fell to Slaanesh’s temptations and became debauched monsters who fight for the thrill of combat and the screams of the dying. The Emperor’s Children field Noise Marines armed with sonic weapons and are known for their speed and the disturbing beauty of their corrupted wargear. Their most infamous champion is Lucius the Eternal, whose curse prevents anyone from truly killing him. Like the other three god-aligned Legions, they now have their own standalone Codex.
6. Iron Warriors
Primarch: Perturabo (Daemon Primarch) | Allegiance: Chaos Undivided | Colours: Silver and gold with hazard striping
The Iron Warriors are the siege warfare specialists of Chaos. Their rivalry with the Imperial Fists defined the Horus Heresy’s greatest sieges, and ten thousand years later, they remain the undisputed masters of breaking fortifications. The Iron Warriors are coldly pragmatic, viewing war as an equation to be solved with firepower, attrition, and expendable slaves. They despise weakness and have no time for the religious fervour of other Chaos warbands, using daemonic technology as tools rather than objects of worship. Their Daemon Primarch Perturabo broods in his fortress of Medrengard, perfecting ever more devastating war machines. They are known for their extensive use of daemon engines, obliterators, and heavy armour.
7. Night Lords
Primarch: Konrad Curze (deceased) | Allegiance: Chaos Undivided (primarily through cruelty rather than worship) | Colours: Midnight blue with lightning bolt motifs
The Night Lords are terror specialists who use fear as their primary weapon. Their Primarch Konrad Curze grew up on the nightmare world of Nostramo and became a brutal vigilante before the Emperor found him. He instilled in his Legion the belief that fear is the most effective tool of control. The Night Lords do not worship the Chaos Gods — many actively despise them — but they have been thoroughly corrupted by millennia of atrocity. They prefer to fight from the shadows, skinning victims alive, broadcasting screams across vox-channels, and striking when the enemy’s morale has already broken. The Aaron Dembski-Bowden Night Lords trilogy is considered some of the finest Warhammer fiction ever written.
8. Word Bearers
Primarch: Lorgar Aurelian (Daemon Primarch) | Allegiance: Chaos Undivided (all four gods equally) | Colours: Crimson red with silver trim
The Word Bearers are the zealots of Chaos — the first Legion to fall to the Dark Gods and the architects of the Horus Heresy itself. Their Primarch Lorgar craved something to worship, and when the Emperor rejected his devotion, Lorgar turned to the Chaos Gods instead. It was Lorgar and his chaplain Erebus who corrupted Horus and engineered the Heresy. The Word Bearers are the most religiously devoted Chaos force, building dark cathedrals, conducting profane rituals, and summoning daemons en masse. They are the most hated of all Traitor Legions because they chose Chaos not out of desperation, madness, or coercion — but out of genuine, fanatical faith.
9. Alpha Legion
Primarch: Alpharius Omegon (status unknown) | Allegiance: Unknown / Chaos Undivided / possibly Loyalist | Colours: Metallic blue-green (hydra scale pattern)
The Alpha Legion is the most mysterious of all Space Marine Legions. Led by the twin Primarchs Alpharius and Omegon, the Alpha Legion specializes in deception, infiltration, and misdirection. Their operatives claim “I am Alpharius” to confuse enemies about their command structure. It remains genuinely unclear whether the Alpha Legion truly serves Chaos, secretly serves the Emperor, or has fragmented into factions pursuing different agendas. They may have betrayed the Emperor to save humanity according to the Cabal’s prophecy, or they may simply be traitors. This ambiguity is the point — the Alpha Legion is Warhammer’s greatest narrative puzzle. They rarely fight as a cohesive force, preferring to use cultists, sleeper agents, and false-flag operations to achieve their unknowable goals.
Major Renegade Chapters and Warbands
Beyond the original nine Traitor Legions, many Space Marine Chapters have fallen to Chaos or gone renegade over the millennia. These are the best-known renegade warbands from Games Workshop’s codexes and campaign books. Many of them are only sketched in a paragraph or two of official background, so treat the short entries as the full extent of what is generally known.
Red Corsairs
Leader: Huron Blackheart, Tyrant of Badab | Allegiance: Chaos Undivided | Origin: Astral Claws Chapter (renegade)
The Red Corsairs are the largest renegade warband, formed from the Astral Claws Chapter after the Badab War. Huron Blackheart leads a pirate empire from the Maelstrom, offering refuge to renegade Marines in exchange for service. They are pragmatic raiders who care more about power and survival than religious devotion to the Dark Gods.
Crimson Slaughter
Allegiance: Chaos Undivided | Origin: Crimson Sabres Chapter (renegade)
The Crimson Slaughter are haunted by the voices of the dead. After the Crimson Sabres massacred a population they believed to be traitors, the Chapter was cursed to hear their victims forever, a torment that only killing seems to quiet. They were the Chaos side of the Dark Vengeance starter set.
The Fallen
Allegiance: Various (some Chaos, some not) | Origin: Dark Angels Legion
The Fallen are Dark Angels who turned on their Primarch during the destruction of Caliban. They were scattered across time and space, and the Dark Angels have hunted them in secret for ten thousand years. Not all Fallen actually serve Chaos, which makes them uniquely tragic figures. Cypher, the most famous of them, carries a sword he never draws, and many accounts suggest he is trying to reach the Emperor on Terra.
The Purge
Allegiance: Nurgle | Origin: Unknown
A warband dedicated to the extermination of all life. The Purge believe the galaxy is so corrupt that only total annihilation can cleanse it, which makes them natural servants of Nurgle’s entropy.
The Scourged
Allegiance: Tzeentch | Origin: A renegade Chapter (original identity not widely documented)
The Scourged were cursed by Tzeentch to hear every lie ever spoken. The endless deception has driven them mad, and they make war in pursuit of a truth they can never be sure of.
The Flawless Host
Allegiance: Slaanesh | Origin: A renegade Chapter (original identity not widely documented)
A warband that fell to Slaanesh through their obsessive pursuit of martial perfection. The Flawless Host believe themselves to be the perfect warriors and fight with arrogant grace, treating every battle as a performance.
The Brazen Beasts
Allegiance: Khorne | Origin: Unknown
A savage Khornate warband, one of the example renegade forces in recent Chaos Space Marine background. Like most followers of the Blood God, they live for close combat and slaughter.
The Cleaved
Allegiance: Khorne | Origin: Unknown
Another Khornate renegade warband from the published background, known for their frenzied brutality in close combat. Little else about them is detailed in official sources.
Sons of Malice
Allegiance: Malal/Malice (a renegade Chaos God) | Origin: Unknown
A deeply unusual warband that worships Malice, a Chaos power that opposes the other Chaos Gods. The Sons of Malice fight against Chaos and the Imperium alike, and are distrusted by everyone.
The Warp Ghosts
Allegiance: Not clearly stated | Origin: Unknown
A warband known for striking without warning and vanishing before the enemy can retaliate, as if they had stepped out of the Warp itself.
The Damned Company of Lord Caustos
Allegiance: Chaos Undivided | Origin: Unknown
A renegade warband named after its leader, Lord Caustos. It appears in older Chaos Space Marine material, but the official background gives little detail beyond its name and its heraldry.
How to Choose a Warband for Your Army
When building a Chaos Space Marines army, your choice of warband primarily affects your army’s lore, colour scheme, and thematic identity. The four god-specific Legions — World Eaters, Thousand Sons, Death Guard and Emperor’s Children — each have their own Codex. The remaining Legions and warbands use the Chaos Space Marines Codex, whose detachments let you lean into different playstyles. In 11th Edition you can combine detachments using Detachment Points, so a warband’s theme can be built from more than one detachment.
For the tabletop, consider what playstyle appeals to you: aggressive melee (World Eaters, Khorne warbands), psychic dominance (Thousand Sons, Tzeentch warbands), durability and attrition (Death Guard, Nurgle warbands), speed and sensation (Emperor’s Children, Slaanesh warbands), or versatile combined arms (Black Legion, Red Corsairs, Iron Warriors). Your warband choice is ultimately about what narrative excites you — the rules can support almost any thematic army.
Frequently Asked Questions
How many Chaos Space Marine warbands are there?
There are 9 original Traitor Legions and dozens of renegade chapters and independent warbands documented across codexes, campaign books, and novels. The total number is effectively unlimited, as new chapters continue to fall to Chaos in the 40k timeline, and Games Workshop encourages players to create their own custom warbands.
What is the difference between a Traitor Legion and a renegade chapter?
Traitor Legions are the 9 original Space Marine Legions that sided with Horus during the Horus Heresy 10,000 years ago. Renegade chapters are loyalist Space Marine chapters that fell to Chaos or went renegade at some point after the Heresy. Traitor Legions tend to be larger, older, and more deeply corrupted, while renegades retain more of their original identity.
Can I make my own Chaos warband?
Absolutely. Games Workshop actively encourages players to create custom warbands with their own colour schemes, backstories, and motivations. There are no special rules needed: you simply paint your army in your own scheme and use the Chaos Space Marines Codex detachments that fit your story. The hobby community has a strong tradition of inventing original renegade chapters and successor warbands.
Which Traitor Legion is the most popular?
The Black Legion is the most popular due to their versatility and prominent role in the narrative. The Death Guard are a close second thanks to their distinctive aesthetic and strong standalone Codex. The Thousand Sons also have a dedicated following for their unique dust-automaton army theme and psychic playstyle.
Why did each Legion turn traitor?
Each Legion fell for different reasons: the Sons of Horus out of loyalty to their Primarch, the World Eaters due to the madness of the Butcher’s Nails, the Thousand Sons because the Imperium turned against psykers, the Death Guard through plague and desperation, the Emperor’s Children through pursuit of perfection, the Iron Warriors from bitter resentment, the Night Lords from their Primarch’s nihilism, the Word Bearers from rejected faith, and the Alpha Legion for reasons that remain deliberately unclear.
What are the Tzeentch Chaos Space Marine warbands?
The Thousand Sons are the great Tzeentch Legion, led by Magnus the Red and his sorcerers. Among renegades, The Scourged are Tzeentch’s best-known warband, cursed to hear every lie ever spoken. Many other warbands mark individual units or champions to Tzeentch while staying broadly Undivided.
Which Chaos Space Marine warbands follow Khorne?
The World Eaters are Khorne’s Legion, led by the Daemon Primarch Angron and famous for Khârn the Betrayer and their Butcher’s Nails. The Brazen Beasts are a notable Khornate renegade warband. Plenty of Black Legion and other Undivided warbands also field units dedicated to the Blood God.
What is the largest renegade Chaos warband?
The Red Corsairs are the largest renegade warband. They were formed from the Astral Claws Chapter after the Badab War and are led by Huron Blackheart from the Maelstrom, where he gives renegade Space Marines from many Chapters a place in his pirate empire. Only the Traitor Legions, led by the Black Legion, are bigger.