Doctor Occult first appeared in New Fun Comics #6 (September 13, 1935).
He was a supernatural detective, whose detecting style was very much in the style of Sam Spade, only with supernatural abilities. He was assisted by his butler Jenkins in one adventure. His girlfriend/partner called Rose Psychic appeared in his first adventure and then returned again later in the series. His given origin was that on New Year’s Eve, 1899, Occult and Rose Psychic had been rescued by a shadowy group called “The Seven” from ritual murder at the hands of a Satanic cult. The two were later trained in the use of occult magics themselves.
Thirty-six years later, Doctor Occult opened up his own detective agency, specializing in crimes of a mystical nature, and during World War II he joined the All-Star Squadron. At some point, he and Rose become fused into one being. Doctor Occult has used sorcery to halt or greatly slow the aging process, so that he appears in modern comics to still be a man in his late thirties or early forties, even though he was born at the end of the 19th century.