A Chaos Space Marine, also sometimes called a Traitor Marine, is a former Loyalist Space Marine of the Imperium of Man 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. Such corrupt Astartes normally belong to one of the 9 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. Chaos can corrupt Astartes of any time and place just as its siren call leads many lesser men to their damnation.