Nightmaster debuted in "Showcase" #82 (May 1969), created by writer Denny O'Neil and artist Jerry Grandenetti. Jim Rook's journey from a rock star to a hero began when he discovered the Sword of Night, which granted him magical abilities and slowed his aging. He defended both Earth and the realm of Myrra from various mystical threats and played a pivotal role in storylines involving the Shadowpact, a group of supernatural heroes.