The Cadian Gate is broken, and the Imperium is riven in two. The might of the Traitor Legions, kept shackled for millennia behind walls of iron and sorcery, has been unleashed on a darkening galaxy. Among those seeking vengeance on the Corpse Emperor’s faltering realm are the Death Guard, once proud crusaders of the Legiones Astartes, now debased creatures of terror and contagion.

On the prison world of Zartak, darkness has fallen on arbitrators and inmates alike. The Night Lords have come, bringing with them the shadow of fear and pain. But these monsters are not the only ones with an interest in Zartak. From the void, running on silent, another fleet emerges. These Space Marine warriors are grey-clad and white-faced, and their eyes are as black as the Outer Dark – the savage Carcharodon Astra.

The Night Lords were once among the most potent forces of the Imperium, Space Marines who used fear itself as their weapon. Now, cast adrift from the Emperor's light and hunted as heretics after their monstrous betrayal, the Night Lords clad themselves in symbols of death and fight the Long War, bringing pain and terror to all who worship the corpse-god of Terra. A summons from Warmaster Abaddon sends these rebels on a dangerous journey that leads inexorably to a conflict with the Emperor's chosen warriors, the Blood Angels.

After seven years of bitter war, the end has come at last for the conflict known infamously as the Horus Heresy. Terra now lies within the Warmaster’s sights, the Throneworld and the seat of his father’s rule. Horus’ desire is nothing less than the death of the Emperor of Mankind and the utter subjugation of the Imperium. He has become the ascendant vessel of Chaos and amassed a terrible army with which to enact his will and vengeance. But the way to the Throne will be hard as the primarch Rogal Dorn, the Praetorian and protector of Terra, marshals the defences.

After seven long years of conflict, the Horus Heresy nears its end. But now, as the Warmaster Horus marches on Terra to rip his father from the Throne, the seat of the arch-traitor’s power lies empty. Cthonia, a world once dominated by brutal murder-gangs, is occupied by the Emperor’s praetorians—the indomitable Imperial Fists. For the Sons of Horus, this outrage demands a reckoning.