Jacob Seneron was a member of the House of Seneron who became a member of the Clergy of Mardük and a close underling of Kareth d'Zarnagon during the Great War. He began wandering aimlessly after the death of Mardük until he found a new purpose serving the Totenkopfs. He was also contacted by the Clergy of Nergal, and Nergal himself eventually used him as a vessel. The possessed Jacob confronted the heroes of the Grand Alliance in the Ruined Kingdom, but he was eventually slain in a brutal battle by Axikasha Keiran who was possessed by Hephaestus.