While the Ultramarines reel from Kor Phaeron's surprise attack on Calth, Lorgar leads the rest of the Word Bearers deep into the realm of Ultramar. Their unlikely allies, Angron and the World Eaters, seem blind to the true goals of the mission, preferring instead to ravage each new civilisation they come across - but where Lorgar might once have chastised his wayward brother, now he seems only to encourage the frenzied bloodletting. Worlds will burn, Legions will clash and a primarch will fall...and the fate of the entire galaxy hangs in the balance.