Space Marines - Traitor Legions: These Space Marine Legions sided with Horus and the Forces of Chaos during the Horus Heresy. After their defeat in the Battle of Terra, these so-called "Traitor Legions" fled into the Eye of Terror and became the primary forces of the Chaos Space Marines.Legion NamePrimarchHomeworldSummaryEmperor's ChildrenFulgrimChemosThe members of this Traitor Legion are the greatest devotees of Slaanesh, the Chaos God of hedonism and dark pleasure. They once sought absolute perfection in every action and appearance, now they fight only to feel the pleasure wrought by suffering and death.Iron WarriorsPerturaboOlympiaThe Iron Warriors are the dark counterpart to the Imperial Fists Chapter. Like the Fists, they are specialists in siege and trench warfare and can build truly labyrinthine static defences. They have an ancient rivalry with the Imperial Fists and all of their Successor Chapters going back to the time before the Horus Heresy.Night LordsKonrad Curze (Night Haunter)NostramoThe Night Lords specialise in the exercise of terror tactics and carrying out atrocities against military and especially civilian personnel that are intended to spread fear in their enemies.World Eaters (War Hounds)AngronNuceriaThe World Eaters devolved into mindless, bloodthirsty fanatics dedicated to the Blood God in the centuries after the Horus Heresy; today they are the chosen ones of Khorne, the Chaos God of violence and murder. They live only to slaughter other living things and shed more blood for the Blood God.Death Guard (Dusk Raiders)MortarionBarbarusThe Death Guard, often better known today as the Plague Marines, are the horrifically diseased and plague-ridden devotees of Nurgle, the Chaos God of disease and decay. They use disease and Chaos-infused toxins and chemical weapons in their attacks.Thousand SonsMagnus the RedProsperoThe Thousand Sons are devoted to Tzeentch, the Chaos God of arcane knowledge and change for its own sake. They are the most adept among the Chaos Space Marines at wielding the dark powers of the Warp and have a large number of Chaos Sorcerers among their ranks. As a result of the ancient curse known as the Rubric of Ahriman, the remaining Thousand Sons Chaos Space Marines have no organic bodies; their souls have been fused directly into their suits of power armour and almost every member of the Legion has at least some psychic ability.Luna WolvesHorusCthoniaThe Luna Wolves were once the premier of the Legiones Astartes, the best of the best among the Emperor's Space Marines. Renamed the Sons of Horus after the Emperor honoured their primarch by making him the Imperium's Warmaster and supreme commander of the Great Crusade after the Emperor returned to Terra following the Ullanor Crusade. After Horus’ death the Sons of Horus became known as the Black Legion.Word Bearers (Imperial Heralds)LorgarColchisThe Word Bearers are the only Traitor Legion to still field Chaplains, who are called Dark Apostles instead and serve as priests of the Ruinous Powers rather than as exemplars of the Emperor's truth; the Word Bearers are highly religious in their mindset and believe deeply in the faith and purpose of the Chaos Gods.Alpha LegionAlpharius OmegonUnknownStrategic subtlety and the employment of covert operations are this Legion's specialty; the Alpha Legion adopted the hydra as their symbol to indicate that their are many ways to accomplish an objective and that if you defeat one of their initiatives there are always others hiding in the shadows. This Traitor Legion may actually still be serving what it believes is the Emperor's will by remaining among the Forces of Chaos; its true motivations remain unclear.Note: The Traitor Legions' homeworlds were later destroyed in a purge by Imperial forces to eliminate all traces of Chaos corruption in the Imperium following the Horus Heresy, with the exception of the Alpha Legion's homeworld, which was never discovered.