When the Beyond Reason Spiritual Fellowship cult invoked the the demon Aan Taanu to Earth, it possessed the dragon Fin Fang Foom and went in a frenzy across China, then attacked New York City. Cult High Priestess Hildreth sought to have an intimate relationship with the demon to allow it to father a race of demonic beings to overrun the earth. The mysterious entity Omen, previously Aan Taanu's servant, incarnated itself on Earth by joining with Charles Blackwater, a lawyer killed by the Cult. Omen renewed him and, using the apartment of Caspar Wright and his great-granddaughter - the young occult genius Ariann - as his base, he gathered several others with occult knowledge: Chan Liuchow, who had stopped Fin Fang Foom in China decades before; writer Martin Gold, former lover of Angel O'Hara (a past human host of Dracula's daughter Lilith); sorceress Jennifer Kale, inheritor of the magic of Atlantean sorceress Zhered-Na; and Katherine Reynolds, former Daimon Hellstrom associate turned unstable mentalist (after developing her powers, Reynolds had been trapped in a mental district by "the Agency," who had increased her abilities with experimental drugs).
Organizing this group into the Legion of Night, Omen brought them to the Astral Realm of Aan Taanu, while Caspar Wright stayed on earth to watch over Blackwater's form. Omen, Liuchow, Reynolds and Kale battled the demon's hordes while Ariann Wright and Gold located the demon's stronghold. Gold restrained Aan Taanu while Ariann tore the demon fetus from Hildreth's womb, killing both mother and unborn child in the process. Aan Taanu then released himself and attacked Ariann, but Omen arrived in time to stick his sword into the demon's skull, either exiling or destroying it. Fin Fang Foom fled into New York Harbor, and the Beyond Reason cult presumably disbanded. The Legion members decided to stay together to defend Earth against further mystic attacks.
Blackwater/Omen and Ariann and Caspar Wright later fought a demon sent by Aan Taanu that had possessed ex-convict Morton Klasser and controlled him into finding Leena Wolfe, a private-eye hired by Klasser's ex-wife to document his affairs and abuses. Upon finding Wolfe, the demon forced Klasser to instead attack Blackwater's ex-girlfriend, Allison Lamb, who had hired Wolfe to investigate Blackwater's behavior changes. Omen, however, had learned of this and temporarily entered Wolfe's form. When Klasser arrived to attack the women, Omen emerged and forcibly took out and killed the demon. Omen told Wolfe she would be called upon in the future to help the Legion in return for rescuing her. While Kale has since affiliated with Satana and Topaz, it is thought that Omen and Ariann Wright continue to assemble the Legion to oppose occult threats. Donna Garth is also thought to have been associated with the Legion.