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.

The Battle Titans of the Adeptus Titanicus are towering war engines, striding to war as holy effigies of the Omnissiah. Greatest of all are the mighty Warlord Titans, their weapons bringing righteous death to alien and heretic alike. Still reeling from a near disastrous battle against tyranids, the Pallidus Morr demi-legio is assigned to a new warzone, a nearby forge world which has fallen under the sway of Chaos.

A Great Hunt has been called, and Kor'sarro Khan, Master of the Hunt, gathers the White Scars for war. They shall track their prey across the galaxy, never resting until his head is taken to be displayed in the Chapter's fortress-monastery on distant Chogoris. But this prey will be a challenge, for he is as fast and as cunning as the sons of Jaghatai and as deadly a foe as the Khan has ever faced. For on this Great Hunt, the White Scars seek the daemon prince known only as Doomrider.

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 Horus Heresy is a civil war on a scale the likes of which the galaxy has never seen before. After the Great Crusade united the disparate worlds of humanity, the very warriors who made it possible turned on each other and tore it apart. Soon after word reached Terra of Horus's nascent rebellion, Mars fell. Set upon by the forces of the Alpha Legion before they had even recovered from the Razing of Prospero, the Space Wolves have been hounded to the edge of the Alaxxes Nebula. In desperation, Leman Russ called out to his primarch brothers for aid. None came.