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Warhammer 40k: Chaos Space Marines 10th edition guide

Warhammer 40k's Chaos Space Marines wreak havoc from the Eye of Terror across the galaxy - here's a guide to lore, tactics, and collecting.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community artwork showing a chaos space marine swinging an axe

Warhammer 40k’s Chaos Space Marines are some of the fiercest, most tenacious, and – ultimately – sinister forces in Games Workshop’s sci-fi universe. While some forces, such as the Imperium or the Eldar, fight desperately against the encroaching tide of Chaos, other Warhammer 40k armies – like these infamous Heretic Astartes – choose to fight for it.

Chaos Space Marines have been a staple of the setting going all the way back to the original Adeptus Titanicus board game. Legend has it the original version of this titanic battling game would have contained Imperium titans facing off against their Eldar counterparts but an issue with the models saw the Eldar being dropped from the box at the last minute.

warhammer 40k chaos space marines guide - Warhammer Community photo showing Iron Warriors havocs models

A hasty bit of rethinking and retooling, along with some new lore, saw the idea of a schism in the Imperium being born. This allowed the box to contain two sets of human-style titans, with one set belonging to the traitorous forces of Horus and his heresy.

We invite you to delve into the darker side of the Warhammer 40,000 universe with us and learn just who the Chaos Space Marines are, where they come from, and how they work in Warhammer 40k 10th edition.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community photo showing chaos space marines fighting imperial guard troopers

Chaos Space Marines 10th edition rules

The long wait is over. Games Workshop has released the Chaos Space Marines Index for Warhammer 40k 10th edition, providing all the rules you need to get started building your force of unholy ruin.

Click here to download your free Chaos Space Marines 10 edition index cards.

We’re working on a new strategy guide for you, but in the meantime here’s a summary of your core options for Chaos Space Marines in 10th edition.

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Chaos Space Marines army rules

The Chaos Space Marines army rules in 10th edition are simple. Whenever you fight or shoot with a Chaos Space Marines unit, you can choose for the unit to gain one of two weapon abilities, either Sustained Hits or Lethal Hits. Both abilities grant you a bonus when you score a critical to-hit roll (usually on a natural six); Sustained Hits grants you an additional hit, and Lethal Hits inflicts an automatic wound.

These provide you with great flexibility when fighting either hordes or high-toughness units like vehicles. However, a unit making a Dark Pact must pass a leadership test afterwards; should it fail, it suffer D3 mortal wounds.

When building your army, ‘The Lost and the Damned’ allows you to include a limited number of World Eaters Khorne Berzerkers, Thousand Sons Rubric Marines, or Death Guard Plague Marines in your army, replacing their faction keyword with Heretic Astartes. They lose any of their own faction abilities, instead gaining the full benefits of being part of your Chaos Space Marine army.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community photo showing Word Bearers Chaos Terminator models

Marks of Chaos are part of the Chaos Space Marine Detachment

The Chaos Space Marines Detachment included in Index Chaos Space Marines is ‘Slaves to Darkness’; it put no restrictions on how you build your army, and provides several benefits.

When you add a unit to your army you’ll give it a keyword representing its devotion to a particular Chaos God: Khorne, Nurgle, Slaanesh, Tzeentch, or Chaos Undivided. There’s a few exceptions: if a unit already has one of these keywords it doesn’t gain another; Psykers can never have the Khorne keyword; and Characters must have the same keyword as the bodyguard unit they join.

Each of these Marks grants that unit an additional bonus when it makes a Dark Pact.

Mark Effect
Khorne In the fight phase, when picking ‘Lethal Hits’ for a Dark Pact, score critical hits on 5+
Nurgle In the shooting phase, when picking ‘Sustained Hits’ for a Dark Pact, score critical hits on 5+
Tzeentch In the shooting phase, when picking ‘Lethal Hits’ for a Dark Pact, score crits on 5+
Slaanesh In the fight phase, when picking ‘Sustained Hits’ for a Dark Pact, score critical hits on 5+
Chaos Undivided Re-roll to-hit rolls of one

The Detachment also provides six 40k Stratagems and five enhancements. The enchancements are each restricted to a Unit with a particular Mark of Chaos, while most of the Stratagems have a greater effect when targeting a unit with a specific Mark.

Enhancement Required Keyword Effect
Talisman of Burning Blood Khorne +1S and +1A to bearers’ melee weapons, or +D3S and +D3A any time the bearer makes a Dark Pact
Orbs of Unlife Nurgle At the end of the fight phase, roll 1D6 for each enemy unit within 6″ of the bearer, or D6+1 if the bearer made a Dark Pact. On a 4+, that enemy unit suffers D3 mortal wounds
Eye of Tzeentch Tzeentch After making a Dark Pact, make a Ld test for the bearer: receive 1CP if passed
Intoxicating Elixir Slaanesh Bearer has feel no pain 5+. After making a Dark Pact, pick one enemy unit attacked: it must make a Battle-shock test
Liber Hereticus Chaos Undivided When making a Dark Pact, unit gains both Sustained Hits and Lethal Hits

Both the Stratagems and Enhancements are restricted to Heretic Astartes units, so if you have a Chaos Knight or Daemons contingent in your force, it won’t benefit.

Stratagem Cost Effect Favored Keyword Bonus effect
Infernal Rites 2CP Pick a Heretic Astartes unit that is targeted by enemy attacks in their Shooting or Fight phase; reduce the AP of enemy attacks targeting that unit by one until the phase ends None None
Profane Zeal 1CP In your Fight or Shooting phase, pick a unit that hasn’t shot or fought yet: it can re-roll to-hit and to-wound rolls of one until the phase ends Chaos Undivided Re-roll all hit and wound rolls
Eternal Hate 1CP Pick a unit that’s targeted by enemy attacks in the Fight phase; models in that unit that are destroyed before they can fight may fight on a roll of 4+ Khorne Add +1 to the roll
Dark Obscuration 1CP Pick a unit after it’s targeted in the enemy Shooting phase; that unit gains Stealth until the phase ends. Nurgle That unit can’t be targeted by enemies unless they’re within 12″
Skinshift 1CP One model regains three wounds Tzeentch Return a (non-character) model to the unit with full wounds.
Unnatural Swiftness 1CP Pick a unit; it can shoot or charge this turn even if it fell back from combat Slaanesh It can also shoot and charge even if it advanced

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Chaos Space Marine Legions rules are gone

At the moment there aren’t distinct rules for all the Chaos Space Marine Legions. The Black Legion, Word Bearers, Night Lords, Iron Warriors, Alpha Legion, Emperor’s Children, Red Corsairs, and Creations of Bile subfactions had their own Traits, Relics, and Stratagems in ninth edition 40k, but for the moment those are all gone. We expect them to return as Detachments when the Chaos Space Marine Codex is released.

Warhammer 40k Beastmen Kill Team models, including a gas mask wearing beastman

Kill Team units are in the index

Both the Traitor Guardsmen Squad and Fellgor Beastmen units make the leap from the skirmish game Warhammer 40k Kill Team in the new Index. Traitor Guardsmen’s ‘Twisted Defence force’ ability grants them the Benefit of Cover while they’re within range of an objective marker, and they have a healthy OC2. Fellgor Beastmen are more dedicated to clearing objectives: they get a 6″ Scouts move after deployment, and get +2″ to Charge rolls when targeting enemies holding objectives.

warhammer 40k chaos space marines guide - Warhammer Community photo showing the new Chaos Cultists HQ unit of minis

A pure Chaos Cultist army is possible

Chaos Cultists are an integral part of many Chaos Space Marine armies, human cattle driven before the advancing marines purely to deplete enemy ammunition and discover their mines. Ninth edition required you to run more Marines than Cultists, despite adding many new units like Accursed Cultists or even the Dark Commune character unit.

Those limitations are gone now and a fully cultist army is possible. Basic Chaos Cultists are a Battleline choice, so you can include six units in your list. Though they have a measly Objective Control value of one, their ‘For the Dark Gods’ ability means that if they do ever control an objective, that objective remains under your control until your opponent can claim it; whether your cultists move on to seek new glory, or are simply exploded by enemy weapons fire.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community artwork showing a Dark Apostle model with attendants

Chaos Space Marines Combat Patrol

When approaching a brand new Chaos Space Marine army, there’ll be a variety of ways to build out a competitive, complete force, which will depend on the way you want to go and what you want to focus on. But the Chaos Space Marines Combat Patrol is a sturdy foundation.

The Chaos Space Marines Combat Patrol contains 19 miniatures, consisting of:  

  • Dark Apostle
  • Dark Disciple x 2
  • Chaos Space Marines x 10
  • Chaos Space Marine Havocs x 5
  • Helbrute

Warhammer 40k Chaos Space Marines faction guide Warhammer Community photo showing a large chaos space marines army fighting Ultramarines

From there, you should look at providing yourself a little defence. What’s more defensive than a meat shield? Nothing, so grab some Chaos Cultists. These won’t do much in either melee or ranged combat, but they will do two thing: draw fire whilst you get your units into position, and hold objectives while your marines take the fight to the enemy. Don’t feel sad about seeing them get mown down; they’re only humans.

When it comes to shooting, you’ll already have some Havocs- which will consistently put the fear of the dark gods into your foe – but for true versatility, you can’t go wrong with some Obliterators. Their Flesh-metal guns can be fired in a variety of configurations against a variety of different targets

Our final recommendation for your starter Chaos Space Marine army is a Chaos Rhino. This transport provides survivability and manoeuvrability, so your marines on board them on board and race to the front as fast as you can.

Just remember: the Chaos Gods are fickle, but, if you do your best to please them, you’ll soon see your opponent’s army burn in the fires of your unholy vengeance.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community artwork showing the Primarch Fulgrim and his legion, the Emperor's Children, before the Horus Heresy

Chaos Space Marines lore

Chaos itself has existed in the setting as long as sentient beings have drawn breath, but for Chaos Space Marines we have to look instead to three select individuals: the Emperor, Warmaster Horus Lupercal, and Lorgar, Primarch of the Word Bearers legion.

The Emperor of Mankind is responsible for creating all Space Marines and their genetic fathers, the Primarchs, so will always be partially behind the creation of Chaos Space Marines. It does appear, especially with some revelations in some of the novels, that the rot which led many Space Marines to the dark side set in exceedingly early.

Humanity’s Emperor may have gained some of the powers and knowledge he used to create the Primarchs from the Chaos Gods themselves – meaning that the fall of many legions of Space Marines may have been inevitable right from the start.

Horus was the fulcrum around which the Chaos Space Marines pivoted from loyalty to heresy. He was the Warmaster of all Space Marines until a combination of hubris, plotting, and a magic knife led him to the welcoming arms of Chaos.

His fall led many other legions to go with him, either manipulated to Chaos’ side, or drawn through promises of power beyond imagination, more often than not aided by Primarchs’ simple hatred of the Emperor himself.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community graphic showing the icon of the Word Bearers Legion

The final architect of the Horus Heresy and the Space Marines’ fall to Chaos was the Primarch of the Word Bearers, Lorgar. A religious zealot who worshipped the Emperor as a god, he redirected his faith to an older power when his fervour was rebuffed by the Master of Mankind.

This saw him embrace Chaos earlier than any of the other Primarchs, leading him to begin seeding traitors throughout his brothers’ legions. It was one of these, Erebus, who oversaw the final corruption of Horus, leading the way to over ten thousand years of endless war.

Other Primarchs joined the ranks of Horus and Lorgar: Magnus the Red and his Thousand Sons; Angron and the World Eaters; Alpharius of the mysterious Alpha Legion; Fulgrim and his perfection-seeking sons, the Emperor’s Children; Perturabo and the Iron Warriors; Konrad Curze of the Night Lords; and, finally Mortarion of the Death Guard.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community artwork showing The Emperor fighting Horus aboard the Vengeful Spirit

Unfortunately for Horus, his uprising did not go quite according to plan. Though he struck down the loyalist Primarch Sanguinius, of the Blood Angels – and dealt a mortal blow to the Emperor – Horus himself was slain, and his fleets and legions splintered, unable to overcome Earth’s defences.

Fleeing into the Eye of Terror, a giant rent in reality caused by the fall of the Aeldari Empire, the traitors escaped the loyalists’ wrath, and continue to plot, plan, and lick their wounds, waiting for a time they will be able to wreak revenge on the Imperium once again.

Though unity has long since fled the Chaos Space Marines (many legions are now little more than pirates or raiders) they still occasionally work together under the direction of the new Warmaster; Abaddon the Despoiler. He and his Black Legion make the core of the blade forever pointed at the throat of humanity, and many Black Crusades have spilled forth from the Eye of Terror to bring ruin to the Imperium under Abaddon’s banner.

Now, in the closing years of the 41st Millennium, the Chaos Space Marines are beginning to reclaim the galaxy little by little. Cadia, the bastion world guarding the Eye of Terror, has fallen, and a vast storm of warp energy has ripped the galaxy in two. This is a time of instability – and it’s a time that Abaddon hopes will see Chaos Space Marines become ascendant over the slowly wasting Imperium.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community artwork showing Abaddon the despoiler leading the Black Legion in battle

Chaos Space Marine Characters

With lore stretching back to the early days of Warhammer 40,000, and many books and releases behind them, there are plenty of Chaos Space Marine characters to choose from. If you’re looking for inventive models that stretch the definition of a Space Marine, you’re looking in the right place. Let’s meet the gang.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community photo showing Abaddon the Despoiler's model for Warhammer 40k

Abaddon the Despoiler

When Horus fell, it was a time of great despair for all Chaos Space Marines – and none felt that despair more keenly than his own legion, the Sons of Horus. Eventually they managed to reform through strength of will alone, and that strength came from one of the Sons of Horus’ most powerful and fearsome warriors: Abaddon.

Blessed by all four Chaos Gods but loyal to none, he leads the reborn and remixed Sons of Horus – now known as the Black Legion and incorporating parts of all traitor legions – in a never-ending crusade against the Imperium. Unlike many Chaos Space Marines, Abaddon the Despoiler doesn’t truly believe in Chaos; he is motivated purely by his great hatred for the Emperor and all those loyal to Him.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community artwork showing Fabius Bile collecting samples

Fabius Bile

While Fabius Bile is certainly a Chaos Space Marine (he was one of the Emperor’s Children legion after all), he has long since strayed from any one legion. Devoted to nothing but his own perverted ideal of perfecting Space Marine flesh, he has become a chirurgeon and scientist without peer, mainly because he’ll conduct experiments no sane person would dare consider.

He travels throughout the known galaxy, always seeking to create a new version of the Space Marine – one better, faster, stronger, more adaptable. With the rise of Primaris Space Marines, he may now have all the new material he’ll ever need to twist Chaos Space Marines into new forms, finally perfecting his life’s work.

Huron Blackheart

Not all Chaos Space Marines fell during the Horus Heresy. Huron Blackheart of the Red Corsairs is a more recent convert. Leader of the loyalist Red Corsairs, he was assigned to patrol the Maelstrom, a much smaller area of warp instability like the Eye of Terror.

Lufgt Huron was not overly devoted to the Imperium, however, and, over time, began to stray from official doctrine. Eventually he led the Red Corsairs in rebellion, taking over the planet Badab and making it his own personal kingdom.

The Imperium noticed – and, after a vicious war known as the Badab War, Huron Blackheart and the Red Corsairs were ousted. Now they make the Maelstrom their home, sending out raids for supplies, pirating nearby shipping lanes, and always working to further Huron Blackheart’s dreams for power.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community artwork showing Lucius The Eternal

Lucius the Eternal

Once upon a time, Lucius was simply a legionnaire of the Emperor’s Children who was exceptionally devoted to mastering the blade. This desire for perfection is common in many of this legion, but Lucius took it to extremes.

After the legion fell to Chaos, he continued his quest, facing down many in single combat to prove that he is the finest swordsman who ever existed. Blessed by Slaanesh, he has unnatural abilities at his beck and call, and, even though he has been slain many times, he always returns, emerging from the skin of the victor like a parasite.

Haarken Worldclaimer, Herald of the Apocalypse

Abaddon the Despoiler cannot be everywhere – so he uses Haarken Worldclaimer as his voice and mouthpiece. If Chaos has a direct human form, it may be in Haarken Worldclaimer, who takes a savage glee in battle, with his vast army of jetpack-borne Chaos Raptors.

You’ll often find Haarken sent ahead of the Black Legion, sowing discord wherever he goes, with fast strikes designed to spread fear and disruption. Though he is not a Night Lord, he weaponises fear much as they would, able to drive his foes to madness and worse through manipulation of terrifying messages and broadcasts.

Khârn the Betrayer

Khârn the Betrayer wasn’t always known by his grim epithet. Once, this World Eater was an intelligent and empathetic warrior who only took pleasure in bloodshed once his terrible, torturous brain implants, the Butcher’s Nails, took hold.

After many lifetimes fighting in the eternal war, countless losses (including his much beloved friend Argel Tal), and seeing his Primarch, Angron, become a Daemon Prince, Khârn has descended into a rage that will never end.

He finally became known as The Betrayer when he, in a frenzy, turned on his own forces, slaughtering scores of them before he could be subdued. Now he is Khorne’s fury incarnate, always where the fighting is thickest, wielding his Primarch’s long-forgotten axe as he hews skulls for the Throne of Skulls and spills blood for the Blood God.