The temple world of Divinus Prim hid from the light of the Astronomican behind an impenetrable curtain that no spaceship could cross. Only Mephiston, Chief Librarian of the Blood Angels Chapter, has any hope of finding out what happened to the once pious world. After performing a magical ritual, Mephiston and his honor guard are transported to an inaccessible planet and discover that a civil war is raging there due to religious differences. The battle is over the Petrified Sword, an artifact allegedly created by the Emperor himself. Yet there is more at play here than just an ideological divide. Mephiston believes that on Divinus Prim he could find the answer to how he became the Lord of Death - the one who harnessed the Black Rage - and perhaps even a way to get rid of the flaw that plagues all Blood Angels without exception.