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.

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 primarchs, nigh-immortal sons of the Emperor of Mankind, take the stage in a series of short stories showcasing some of their great deeds and hideous acts from across the Great Crusade and the Horus Heresy.

The Night Lords are among the most feared Chaos Space Marines in the universe. They prey on their victims from the shadows, stalking the faithful of the False Imperium in their ultimate quest to destroy the Emperor. The warband of the Exalted, travelling aboard The Covenant of Blood, are recovering from the events at Crythe Primus. But their dark crusade against the loyal Imperial forces continues, and they will leave a trail of blood and terror behind them as they seek the truth behind the death of their primarch, the feared Night Haunter.

Blade of Purity contains two linked tales of the Grey Knights: Incorruptible and True Name.