Eidel was an officer in the SS, and a member of Adolf Hitler's inner circle. He enjoyed flaunting his authority over others. As a result, Colonel Dietrich disliked him; as well as the other black-uniformed SS thugs who thought they ran the world. It was Eidel who assigned Dietrich the all-important task of recovering the Ark of the Covenant, and also told him to hire the Frenchman Belloq.
Eidel only appears in Campbell Black's novelization of Raiders of the Lost Ark.