"After the cancellation of his Fourth World titles at DC, Jack Kirby created a number of other properties for the company, none of which survived very long. One of these was the Demon, conceived as the demonic alter-ego of Jason Blood. Kirby borrowed the Demon’s look from a Prince Valiant comic strip in which that character donned a demon costume.
In contrast with Kirby’s Fourth World work, his work during this period often blended genres in ways that can sometimes seem strange or arbitrary. Kirby’s The Demon mixed the supernatural and super-heroes. It may be seen as a noble experiment, in as much as it was essentially a supernatural title marketed for the super-hero audience. But Kirby’s super-hero aesthetics proved a strange mix, undermining the seriousness of the supernatural elements.
The series lasted only 16 issues, but the Demon would begin appearing occasionally across the DC Universe, only a few years after his title’s cancellation. He would be more substantially revived in the 1980s, and he’s become a staple of the DC Universe ever since." - quote source