Having fought during the devastation of Baal, Mephiston and a cohort of Blood Angels are drawn by cryptic visions to a war-torn world on the cusp of the Great Rift. Here, the sorcerers of the Thousand Sons seek to unite nine Silver Towers and bring about a ritual that will empower their master, the daemon-primarch Magnus. The ritual must be prevented, lest the entire sub-sector be cast into Chaos. Mephiston faces a challenge like no other, of his strength and his will, confronting a hidden truth that threatens to expose him to his darkest fears.