After learning on what Arthas had done, William was able to survive his wrath and made his return trip to Lordaeron, but when he returned, he witnessed a Death Knight killing Vivian and threw an amulet that she gave Thassarian before he left to travel to Northrend. William believed that this was the death knight who killed his friend Thassarian, but he did not realize that the Death Knight was actually his best friend. Years later, William volunteered to join the Valiance Expedition that settled in Northrend and would soon learn that his friend Thassarian had in fact survived.