The great Forgemaster of the Imperium has disappeared. Her personal forge, the Crucible of Allyn, erupted in a conflagration that consumed its host city overnight. Now her children have risen in rebellion against the Empress, guided by an unseen hand known only to Imperial citizenry as the Cabal. The Books of the Forge, a set of seven texts the Cabal claims to have been authored by the great Forgemaster, have emerged as weapons used to turn brave, loyal citizens into slavering hounds baying for blood and fire.