Josef Mueller was a German Luftwaffe pilot abducted from 1945 by Venger using the Crystal of Chronos. Josef is found by the heroes and befriends them. He is astonished by the Realm and then elated when the heroes tell him that World War II is over as he hated the war and Hitler. When Venger makes a pact with Josef to return him home on the condition that he helps the Nazi's win the war with the jet fighter of Starfire One-Niner he pretends to agree but uses the plane's weaponry to attack the crystal and then destroys it completely by crashing the jet into it before ejecting and parachuting home through the portal.
Dungeon Master assures the heroes that time has not been altered radically and that Josef has defected to fight alongside the allies.
Josef's surname was originally going to be Wulf but was changed for something less Germanic-sounding.