A Chaos Space Marine, also sometimes called a Traitor Marine, is a formerly loyal Space Marine who has chosen to betray the service of the Emperor of Mankind and dedicate his soul to the service of Chaos and its foul deities. Traitor Astartes either belong to one of the 9 Traitor Legions while other traitors come from Space Marine Chapters that have turned Renegade. Chaos Space Marines are proof that not even the Emperor's Finest are immune to the seductions of Chaos.
Chaos Spaces Marines originated in the Galaxy wide Civil War known as the Horus Heresy that saw nine of the eighteen Astartes Legions turn away from the Emperor's light, led by their Primarchs. The traitors were led by Horus Lupercal, the Emperor's most favoured son. The Imperium eventually triumphed at the Battle of Terra where Horus was obliterated and the Emperor mortally wounded. The traitors fled into the Eye of Terror to escape the Imperium's wrath. The nine Traitor Legions are the Black Legion, the Emperor's Children, the Death Guard, the Iron Warriors, the Night Lords, the Thousand Sons, the Word Bearers, the World Eaters and the Alpha Legion. The Traitor Legions either dedicated themselves to a single Chaos God or Chaos Undivided, although no one knows in the Alpha Legion's case. The Emperor's Children serve Slaanesh, the Death Guard serve Nurgle, the World Eaters serve Khorne and the Thousand Sons serve Tzeentch while the Black Legion, Night Lords, Iron Warriors, Word Bearers and (possibly) Alpha Legion serve Chaos Undivided.
The Traitor Legions are the most powerful of the Forces of Chaos. The flesh and Power Armour of Chaos Space Marines often warps and twists into new, darker and inhuman forms under the influence of the Chaos 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, but above all else the power to rule their fellow men in the name of the Chaos Gods, is the driving ambition and goal of every Chaos Space Marine.
Chaos Space Marines are similar to Space Marines in that they have similar troops and vehicles but aren't as flexible and more geared towards close combat. Just like Loyalist Astartes, Chaos Marines are quite expensive to train and reinforce so it's a good idea to have a stable economy. Chaos Marines can also choose to dedicate themselves to a single god to unlock units and upgrades, you dedicate to a god by selecting one of the four Marks, you can only pick one Mark and picking one will make you unable to access the units of another God, for example, picking Khorne will make you unable to use noise marines while picking Tzeentch makes you unable to use Nurgle units and vice versa.
Picking a Chaos God influences your play style. The Mark of Khorne is very melee oriented, his dedicated unit being Khorne Bezerkers, the Khornate Champion, Khornate Terminators and the Bloodthirster. While weak in range, once in melee Khornate units will rip and tear until there's nothing left. Picking this Mark denies you Slaanesh units
The Mark of Nurgle unlocks the Plague Marines, the Nurgle Champion and the Great Unclean One. Despite looking like rotting corpses, Nurgle units can soak up heavy amounts of firepower while dishing it out in return. Mark of Nurgle also unlocks the Rot Spewer, a Nurgle corrupted Baneblade that fires plague bile. Picking this Mark denies you Tzeentch units.
Mark of Tzeentch are those who like using sorcery. Picking this mark unlocks the Rubric Marines, the Aspiring Sorcerer and the Lord of Change. Rubric Marines are slow and expensive but have high hit points and deadly weaponry, they can also reinforce to 8 squad members and their sergeant, an aspiring sorcerer, makes them move faster. Picking this mark denies you Nurgle units.
The Mark of Slaanesh unlocks Noise Marines, Slaanesh Champion and the Keeper of Secrets. Noise Marines are effective against infantry, morale and structures. Slaanesh units are good at breaking morale and slowing down enemies. Picking this mark denies you Mark of Khorne.
Chaos Space Marine vehicles are similar to Loyalist vehicles however Chaos Marines don't have access to the varied types of land raiders and dreadnoughts, only have the regular land raider and dreadnought. They also lack land speeders, whirlwinds, stalkers, Damocles and razorbacks, (this is justified in 40k lore that CSM don't have access to these as they were developed after the Horus Heresy). Instead, Chaos Marine vehicles are more assault oriented and have unique vehicles such as the defiler and Deathwheel.
Chaos Space Marines can also use the foul entities of the warp. While they do not have access to daemons as they are their own faction, they can call forth greater daemons and have access to Possessed, Obliterators and Mutilators.
Overall, Chaos Space Marines are assault oriented, while lacking the flexibility of their loyalist counterparts, CSM make up for this with better offensive forces, meatshields and using the warp.
Technology Tree Edit