The New Mutants

Only the blackest of hearts would dare delve into the dark magic of the Elder Gods, but 13th Century sorcerer Belasco was of just such a heart. He promised to help these evil gods return to Earth in exchange for vast mystical power and nigh immortality. The Gods agreed, but their power left a mark. Belasco became like unto a demon himself, and the father of a race of new demons. The ritual to bring the Elder Gods to Earth involved five mystical bloodstones, but it must have never been completed or was disrupted– the actual details remain lost to the ravages of time.

Villain Group
Demons of Limbo