Diablo was an evil alchemist who had been confined by the good alchemist Andrea Vecchiato to a "tower with no door" in 15th century Milan. Along with the help of his hunchback henchman Peppone, he reached across time to kidnap people close to the Fantastic Four, only to challenge them to a contest. He intended to use Reed's sister, Enid, as an important part of his plan for immortality. The Four, along with a contingent of soldiers led by Willie Lumpkin, went back in time to oppose him. He was defeated and vanished after being touched by Reed's temporary super-powered sister Enid.