Berlin, Early 1600s
While not much is known about Zettler, what is known is that he acted as a Nazi doctor at Auschwitz. Before, he was rumored to have been a witch-hunter and a Hessian mercenary, greatly interested in medical atrocities, but his embrace only furthered his insanity and depravity. He has served the Urge-Wyrm of Cruelty for at least sixty years. Zettler is also an extremely affluent Sabbat Cainite; his affluence comes from his position as the director of the Special Projects Division within the secretive megacorporation known as Pentex.
He was placed on the board of directors in a partnership between Pentex Incorporated and the Sabbat that formed in 1945. He is the the Division director of the SPD, which includes such projects as Iliad and Odyssey, but he also has a finger or two in many more enterprises, such as the Panacea Pharmaceuticals.
It is implied that Harold Zettler is a great deal older than the Third Reich or Pentex. During the Dark Medieval, a Malkavian named Harold the Zettler was part of a Hessian bloodline of Malkavians that delved into Dark Thaumaturgy in order to find a way to aid the Salubri against the Thaumaturgy of the Tremere. The Malkavians learned their arts from servants of a three-headed Dragon, which is likely the Wyrm. The Zettler betrayed the entire bloodline to the dragon in exchange for mastery over their speciality Path and soon disappeared from Cainite society. His writings, however, remained, tempting several german vampires into infernalism.