Once, they were the defenders of the Imperium. Now, the Traitor Legions seek to destroy it in service of ancient, malefic deities. 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, mayhem, but above all else, the power to rule their fellow Humans in the name of the Chaos Gods.
The gifts bestowed by the Dark Gods for their loyalty are fickle indeed: arms reshaped as axes of bone, or the face of a slavering hound. Even the ungifted are changed under the influence of the Warp; their shapes morphed to embody the Astartes' new, corrupted allegiance.