Baron Fernando von Soozle is the eponymous Witch Hunter of the episode The Witch Hunter.
He is not the only Witch Hunter however, as in The Good the Wicked and the Silver he is joined by three others who with him form the League of Witch Hunters.
His debut involves some question as to how to pronounce/spell his middle name. He initially says it like "van" but later shifts to sounding like "von" or "vaughn" and Wilhelmina Witch notices this and corrects him on it.