 The Librarian finds Endurance-of-Will, a Promethean and former love interest of the Ur-Didact.Endurance reveals that the Ur-Didact is using the essences of the composed humans and Prometheans to build an army of mechanical Promethean Knights, with which he plans to defeat the Flood and eradicate all species who might challenge the Forerunners in the future.Despite resenting her for being chosen by the Ur-Didact instead of her, Endurance is eventually convinced to help the Librarian take down the Ur-Didact and seal him in a Cryptum.