When the Beyond Reason Spiritual Fellowship cult summoned the demon Aan Taanu to Earth, it possessed the dragon Fin Fang Foom and rampaged across China, then attacked New York City. Cult High Priestess Hildreth sought to mate with the demon to allow it to father a race of demonic beings to overrun the earth. The enigmatic entity Omen, formerly Aan Taanu's slave, manifested on Earth by merging with Charles Blackwater, a lawyer slain by the Cult. Omen resurrected him and, using the apartment of Caspar Wright and his great-granddaughter - the young occult prodigy Ariann - as his base, he gathered several others with occult experience: Chan Liuchow, who had foiled 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 imprisoned in a mental ward by "the Agency," who had amplified 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 remained 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, slaying both mother and unborn child in the process. Aan Taanu then freed himself and attacked Ariann, but Omen arrived in time to plunge his sword into the demon's skull, either banishing or destroying it. Fin Fang Foom fled into New York Harbor, and the Beyond Reason cult presumably dissolved. The Legion members elected 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 manipulated him into locating Leena Wolfe, a private investigator hired by Klasser's ex-wife to document his affairs and abuses. Upon locating 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 removed and slew the demon. Omen told Wolfe she would be called upon in the future to assist the Legion in return for saving her life. While Kale has since affiliated with Satana and Topaz, it is believed that Omen and Ariann Wright continue to assemble the Legion to oppose occult threats. Donna Garth is also rumored to have been associated with the Legion.
An empath and savage fighter, Katherine can sense magic, and her soul-kiss/mind-meld - allegedly so twisted that Hell looks good by comparison - can incapacitate demons. Omen can teleport, communicate telepathically, sense demonic forces, and use a magic sword. Ariann has innate magical understanding, limited precognition and prescience, and she can combat magical beings and speak to shadows and souls. The others lack inherent powers, using instead experience, intuition, and their wits.