The Ghosts are sent to the Shrineworld Hagia, religious capital of the Sabbat worlds and homeworld of the revered Saint Sabbat herself, to reclaim the holy world from the clutches of Pater Sin and his so-called "Infardi". During their campaign to reclaim the Doctrinopolis – the planet's central city – Gaunt, who has command of the ground forces, is forced into a trap set in one of the most holy structures in the city. A warp-beacon is activated in the process, and a Chaos fleet advances on Hagia to obliterate the Imperial forces.