The Dark Angels have suffered great losses, but have also won new information about the identity of the Fallen, the ancient, Chaos-tainted figure who has puppeteered their every move since they arrived in the Calaphrax Cluster. The scene is set for a bloody collision between the Dark Angels, hiding the secrets of their past, Inquisitor Sabbathiel, ruthlessly bent on exposing their crimes at all costs, the fearsome Grey Knights, who will brook no heresy, and the forces of Chaos, who rain fire on the just and unjust alike. A ferocious battle is soon joined!