The next novel in the ground-breaking, bestselling series that tells the story of the Horus Heresy – the civil war that nearly tore the human Imperium apart, ten thousand years ago. This novel explores the early history of the Dark Angels Legion and their Primarch Lion El'Johnson. When news of Horus's treachery reaches Caliban, the loyalties of this proud and mysterious Legion are tested to the limit, wth tragic consequences.