Faction Files: Chaos Space Marines — Lore of the Long War

Ten thousand years ago, the finest warriors humanity ever forged marched on Terra to burn down the empire they had built. They lost. And here is the terrifying part: they never surrendered, and they have not stopped fighting for a single day since. That grudge has a name — the Long War — and it is still going.

Welcome back to Faction Files, our series prising apart the lore of Warhammer 40,000 one faction at a time. No dice, no meta, no points-cost grumbling — just who these lot are and why. Today: the traitor Space Marines who serve the Dark Gods, and the galaxy's most spectacular fall from grace. Fancy raising a warband of your own? The Chaos Space Marines collection is right this way.

FILE 01 // Origins: the knife in the Emperor's back

To understand the Chaos Space Marines you have to go back to the worst civil war in human history. The Emperor built twenty Space Marine Legions to conquer the galaxy in His name, each handed to a genetically engineered demigod son — a Primarch. It worked beautifully, right up until His favourite son, the Warmaster Horus, was corrupted by the Chaos Gods and turned half of that army against Him.

The result was the Horus Heresy: brother against brother, Legion against Legion, ending with a final desperate assault on Terra itself. Horus was slain, the rebellion broke, and the surviving traitors fled — hounded into the Eye of Terror, a warp storm where reality and the immaterium bleed together. Nine Traitor Legions went in, and none ever forgave. Browse the whole rogues' gallery in the wider Warhammer 40k Chaos range.

FILE 02 // The Long War: a grudge that outlived empires

This is the thing that makes Chaos Space Marines what they are. They are not raiders after loot, nor cackling cartoon villains. They are the losing side of a war they have never accepted was over. The Long War is their whole identity — an eternal campaign of vengeance against the Imperium that cast them out.

And time works strangely for them. Inside the Eye of Terror the warp does not keep honest hours: while ten millennia crawled past outside, some legionaries have lived only a fraction of that, and others far more. A handful of the traitors fighting the Imperium today marched on Terra in person. That is the horror of the Long War — a grudge so old it predates every living thing your enemy has ever known, and it simply will not end.

FILE 03 // How they wage war: raiders, rivals and ruin

Forget the disciplined battle-line of their loyalist cousins. Chaos has no single empire and no chain of command worth the name — just countless warbands, each a Chaos Lord and his followers, carving out power, settling old scores, and as happily knifing a rival warband as an Imperial one. Chaos is its own worst enemy as often as anyone else's, which is precisely why it has never simply steamrolled the galaxy.

What they lack in unity they make up for in malice and firepower. These are still Space Marines — superhuman, power-armoured, veterans of ten thousand years of butchery — now armed with daemon-forged weapons, warp sorcery and the gifts of gods who reward cruelty. They strike out of the Eye of Terror, gut a world, and vanish before the Imperial Navy can respond. And every so often they stop bickering long enough to do something genuinely apocalyptic — which brings us to the one warlord who can make them march as one.

FILE 04 // Abaddon and the Black Legion: the Despoiler's crusades

If Chaos has a face, it belongs to Abaddon the Despoiler. Once first captain of Horus's own Legion, he refused to let the dream die — reforging the shattered remnant into the Black Legion and taking up the mantle of Warmaster. When Abaddon speaks, even the proud rival Legions listen, because he alone can unite the warbands for a Black Crusade: a full-scale invasion boiling out of the Eye of Terror.

His thirteenth was the big one. The 13th Black Crusade shattered the fortress-world of Cadia, the Imperium's great bulwark, and in the aftermath the Great Rift tore the galaxy in two, plunging half the Imperium into darkness and isolation. It is the single most successful blow Chaos has ever landed. Abaddon, it turns out, was not bluffing after all.

FILE 05 // Why collectors love them

Good news for the hobbyist: no faction gives you more creative rope than Chaos Space Marines. The whole point of a warband is that it is yours — your colours, your icon, your patron god, your story. No wrong answers, because Chaos is chaos.

• Paint them any way you like: grim gunmetal and rust, or dedicate the lot to a single Dark God — brass and blood for Khorne, plague-green for Nurgle, shifting blues for Tzeentch, decadent purple for Slaanesh.
• Conversion heaven: spikes, skulls, trophies and mutations mean no two models need look alike — this is the range where kitbashers lose entire weekends.
• Gateway to a whole side of the setting: from the undivided warbands you can branch into the cult Legions like the World Eaters, Death Guard and Thousand Sons, or summon in some Chaos Daemons for backup.

New to all this? Our beginner's guide to Warhammer 40k covers the fundamentals, and the full Chaos Space Marines collection is waiting whenever the Long War calls.

Threat assessment

Few things keep the High Lords of Terra awake like the traitors at the gate. Chaos Space Marines know exactly how the Imperium thinks, fights and prays — because they helped design it. They are its own weapons turned inward, wielded by warriors who have had ten thousand years to sharpen their hatred and not one reason to soften it. The only mercy is that they despise each other almost as much as they despise you. Almost.

Final thought: the Tyranids want to eat you and the Necrons want to file you under paperwork, but the Chaos Space Marines want something worse — to prove they were right all along. That is what makes them the setting's most human villains. They fell exactly the way any of us might have.

Further reading: crunch the numbers with our Chaos Space Marines: Army Analysis, or get the lay of the land in the Warhammer 40k Factions Hub.