The war for the fate of mankind blazes on. Though the outer defences have fallen, the walls of the Imperial Palace itself remain inviolate as Rogal Dorn, the Praetorian of Terra himself, uses every known stratagem and ploy to keep Horus’s vast armies at bay. In Perturabo, the Traitor siegebreaker, Dorn faces an adversary worthy of his skill. The crucial battle for the Lion’s Gate space port is at the heart of this conflict. With it in their possession, the Traitors can land their most devastating weapons on Terran soil.