Chaos Space Marines

Chaos Space Marines, also sometimes called Traitor Marines, Renegade Marines, or Heretic Astartes, are former Space Marines of the Imperium of Man who have chosen to abandon the service of the Emperor of Mankind and dedicate themselves to Chaos to achieve their own ends.

Such corrupt Astartes usually belong to one of the nine original Traitor Legions that betrayed the Emperor during the ancient civil war called the Horus Heresy more than 10,000 standard years ago, while others come from Space Marine Chapters created long after the Heresy ended that have turned Renegade. Chaos can corrupt Astartes of any time and place just as its siren call leads many lesser men and women to their damnation.