Warhammer 40k: Chaos Space Marines 9th Edition guide

Warhammer 40k's Chaos Space Marines wreak havoc from the Eye of Terror across the galaxy - here's our 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, in the 41st millennium, throws a wide net over malcontents, wizards, heretics, and many others who choose to throw their lot in with dark gods. Some come to Chaos to learn forbidden knowledge, others for power, others for freedom from restrictive rules. No-one is immune to the siren song of Chaos – not even, of course, the Imperium’s elite guardians: the Space Marines.

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. 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.

Whatever their beginnings, Chaos Space Marines have become one of the most well represented forces in Warhammer 40k. From the tabletop to fiction, the superhuman power-armoured warriors of Chaos have become almost as iconic as their imperial counterparts.

And, with a brand new 9th edition Chaos Space Marines codex to play with, they’re finally a flexible, competitive tabletop army once again.

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 play on the tabletop battlefield.

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 as the Betrayer. 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.

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

Chaos Space Marines codex



The long wait is over. Up for pre-order on June 25, 2022 and released on July 2, the 9th edition Chaos Space Marines codex is now alive and kicking, and we can get up to speed on the long war.

A Codex arrival is often a tumultuous affair, and this enhanced Chaos Space Marines Codex was no different, with a ton of changes which may completely alter how you approach your traitorous army. Here’s some of the big stuff from the new Codex:

warhammer 40k chaos space marines guide - Warhammer Community photo showing a Black Legion chaos space marine legionnaire model

Chaos Space Marines get two wounds each

That’s right, your basic marines – Chaos Space Marines Legionnaires – now get two wounds. Finally, every CSM player can let out a sigh of relief. A long-deserved base upgrade for the heretics, it gives them a much-needed fundamental uplift to their survivability on the table.

Also, it means people can stop going on about it all the time.

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

Marks of Chaos are Back

In 8th Edition, Marks of Chaos simply aligned your units with a Chaos God, allowing certain spells or rules to affect them. Now Marks of Chaos have a power and points cost, and they don’t just only attach rules keywords to a unit or model; they grant them useful in-game abilities too.

This means your choice of chaos god patron for your army  – Khorne, Nurgle, Slaanesh, Tzeentch, or Chaos Undivided – matters more than ever before, and it’ll change how your army performs on the battlefield.

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

Legion identities are a big thing now

With this new codex, Games Workshop has doubled down on giving each Chaos Space Marine Legion a different playstyle and feel from those of its peers. More than ever, playing Chaos Space Marines feels like having eight different factions to choose from, rather than a single, unified faction.

Inside the codex you’ll find rules for Black Legion, Word Bearers, Night Lords, Iron Warriors, Alpha Legion, Emperor’s Children, Red Corsairs, and Creations of Bile. Each subfaction has its own Traits, Relics, and Stratagems setting it apart from its traitorous siblings.

For example, Abaddon’s Black Legion Trait sees them ignore modifiers to Combat Attrition test rolls, as well as giving them a +1 to hit when shooting at the closest eligible unit, or when making a melee attack after a charge.

Compare this to the Iron Warriors, who strip opponents of cover bonuses when attacking, and can mitigate incoming attacks’ Armour Piercing effects, and you begin to see just how differently each Legion now plays.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community artwork showing a khorne berzerker

Let the Galaxy Burn

Death to the False Emperor is dead; long live its replacement, Let the Galaxy Burn – a rule applied if every unit in your army has the Traitoris Astartes keyword and they’re all from the same Legion. It’s a meaty rule that has two potentially game-changing effects.

The first applies to flamers, giving a +2 to the result when determining how many of those auto-hitting flame attacks are made. Things are suddenly going to get very hot for your opponents.

But the second – and biggest – portion of Let the Galaxy Burn comes in the form of the Chaos Space Marines’ equivalent to the loyalist marines’ ‘Combat Doctrines’ – titled Wanton Acts.

warhammer 40k chaos space marines guide - Warhammer Community photo showing Black Legion chaos space marine legionnaire models

In the first Battle Round of a game, your army will be engaged in Wanton Destruction, which grants an extra hit for each unmodified hit roll of six (a.k.a. exploding sixes) with Heavy, Rapid Fire, and Grenade weapons. In the second round, you’ll move into Wanton Massacre, where the same applies, but for Rapid Fire, Assault, and Pistol weapons. Finally, in the third round, you can choose between Wanton Massacre and Wanton Slaughter – the latter then becoming mandatory for the fourth and fifth Battle Rounds.

Perfect for the melee-fighty stage of your battle plan, Wanton Slaughter gives exploding sixes for Assault, Pistol, or melee weapons. Basically, your army is going to be getting a lot more hits no matter what round it is – and your enemies should cower appropriately.

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

Everyone loves Cultists

Chaos Cultists are an integral part of many Chaos Space Marines armies, and, in the 9th Edition codex, that’s been recognised. Not only are they getting a model refresh – with frankly beautiful new zealots to populate your battle – they’re also getting backup in the form of daemonically twisted Accursed Cultists and the dedicated Cultist HQ unit Dark Commune.

This is balanced out by a restriction on the amount of Cultists units you can take, with them prohibited from outnumbering Traitoris Astartes Core Infantry (your proper chaos marines). This means you can’t run a Cultists-only army… at least for now.

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

There’s tons more to uncover in the 9th Edition Chaos Space Marines Codex, from new Psychic Powers and Prayers, to rejigged datasheets for many units. There are a few niggles for some fans, such as the lack of custom Legions (you have to simply copy the Legion that best matches your intended playstyle), the removal of some wargear options for popular units (jump packs for Chaos Lords are a thing of the past), and some Dark Hereticus Discipline powers feeling a little… underpowered.

Overall, though, this is a strong Codex which looks to add flavour back into one of the zestiest factions in the game – as well as some rules which should have your local Chaos fan rubbing their hands with glee.

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

How to start collecting Chaos Space Marines

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. Still, there are a few basics that every Chaos Space Marine army can benefit from, so let’s take a look at them.

Firstly we’d definitely recommend getting your hands on the revamped Start Collecting! Chaos Space Marines box. This contains a Master of Possession, a Venomcrawler, two Obliterators, two Greater Possessed, and a unit of ten Chaos Space Marines. This is an incredibly versatile box, giving you access to Psychic abilities, a strong vehicle, two of the best shooting models that Chaos Space Marines have access to, two powerful melee models, and a standard workhorse squad of the main guys themselves: the Chaos Space Marines.

Warhammer 40k Chaos Space Marines faction guide Warhammer Community photo showing Khorne berzerker models

From there, you should look at providing yourself a little defence. What’s more defensive than a meat shield? Nothing, so get grabbing some Chaos Cultists. These are a horde unit and won’t do much in either melee or ranged combat, but they will do one thing: they’ll draw fire whilst you get your units into position. Don’t feel sad about seeing them get mown down; they’re only humans.

As we mentioned above, when it comes to melee, you can’t do better than Berserkers or Possessed. Berserkers make a truly unholy number of attacks with chain axes when they get into close combat, whilst Possessed have great synergy with the Greater Possessed from your Start Collecting! box. Choose either, or both! Indulge yourself; it will please Slaanesh. When it comes to shooting, you’ll already have some Obliterators – which will consistently put the fear of the dark gods into your foe – but, for true versatility, you can’t go wrong with some Havocs. These are your heavy weapon troops, and can come equipped with a wide array of weapons, meaning you’ll have some swiss-army-knife ranged support for your battlefield adventures.

To build out some character in your force, we’d recommend looking at a Sorcerer with Jump Pack, to be able to take advantage of more Psychic abilities while zipping around the board, giving Warptime to your troops in unexpected places, and keeping your opponent on their toes. In addition, a Dark Apostle is an essential purchase, as they give your army access to lots of buffs and effects through their prayers – which can help make your force more competitive.

Our final recommendation for your starter Chaos Space Marine army is a Chaos Rhino. What good is a melee unit if you can’t get it into melee? This transport should see your survivability improve somewhat, especially if you’re using Berserkers – so stuff them on board and race to the front as fast as you can.

From there on, what you purchase will depend on which legion you’re intending your army to be from. For a Word Bearers army, you may want to focus on daemonic troops, such as more Possessed, or even dipping a toe into actual Chaos Daemons. For Night Lords, you could be looking at some Warp Talons and Raptors to divide up your enemy’s forces with rapid attacks. Or, if you’re looking at making a World Eaters army, you’ll want more Berserkers. A lot more Berserkers. And then even more Berserkers.

Now you should be more acquainted with the fearsome, fun-loving chaps who make up the Chaos Space Marines, with a few ideas of what to watch for on the battlefield, and who you might want to pick up when building a force. 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.