The Realm of Beasts has ever been a place of savagery and destruction, defiant in the face of Sigmar's feeble attempts at liberation. But now, deep within the mountains of the Ghurish Heartlands, something ancient stirs. A god long-trapped is about to awaken, and the drumbeat of war calls. Ferocious Ironjawz, gluttonous Ogors and towering gargants all set their sights on the human interlopers, determined to cast down their keeps.

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.

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. The Siege of Terra looms, and the fate of the galaxy balances on a razor's edge.

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. This war was not only fought on a galactic scale – it was contested a million times over in brutal battles between former brothers and allies. Since the near-destruction of the Iron Hands, Raven Guard, and Salamanders on Isstvan V, scattered warbands from these 'Shattered Legions' have waged a guerrilla war on Horus' forces across the galaxy.