For Ianthe, war is all too familiar. A former soldier in the Astra Militarum, she now serves Inquisitor Covenant as an agent of the Throne. Her first mission sees her investigating a cult called the Children of Eternity. Falling foul of the local Enforcers, Ianthe soon learns that war in the shadows is seldom straightforward and that the local, angry law-keepers are the least of her troubles.

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.

For many long years, the ork warlord known as the Overfiend of Octarius has bedevilled the Imperium, ruling his alien empire in the heart of the Emperor's realm. Now, at last, three Chapters of Space Marines come together to destroy the greenskin menace and restore Imperial rule. The Salamanders, White Scars and Raven Guard, together with their allies from the Astra Militarum and bolstered by the aid of the mercurial alien eldar, fall upon the worlds of Octarius system with chainsword and bolter, bringing death to the orks.

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.

On the forge world of Morod, the machines never stop and the work never ends. The population toils in the mines and factoria to protect humanity from the monsters in the void, while the Adeptus Mechanicus enjoy lives of palatial comfort. Genetor Gammat Triskellian seeks to end this stagnant corruption. When he learns of a twisted congregation operating within the shadows, one which believes that the tech-priests are keeping people from their true salvation, he sees in them an opportunity to bring down Morod's masters and reclaim the world in the name of progress.