Wilhelm III was the Grand Theogonist during the time of the First Vampire War, who was instrumental in the destruction of Vlad von Carstein, the First of the Vampire Counts. Little is known of Wilhelm other than the fact that he was present during the Siege of Altdorf in 2051 IC. In search of divine aid, the Grand Theogonist retreated into the catacombs of the Cathedral of Altdorf to pray. It was in that holy place that he received a visit from Mannfred von Carstein, the eldest thrall of Vlad.