Perturabo is a master of sieges and an executioner of Olympia. For a long time he lived in the shadow of his more privileged brothers-Primarchs—disappointed by the worldly and shameful duties that regularly fell to his Legion. When Fulgrim offers him the chance to lead an expedition in search of ancient and devastating xenos weaponry—the Iron Warriors and the Sons of the Emperor unite, embarking on a risky venture deep in the heart of a stellar maelstrom, following Perturabo’s dreams. Hunted by those seeking revenge and by the ghosts of a dead Eldar world on Istvaan-V, they must act quickly if they want to free the destructive force of the Angel Exterminatus!