Over 21 millennia ago, the demon Zarathos preyed on mankind, a legend even amongst his own kind. Coveting the mystical Medallion of Power, he was opposed by the Blood, humanoid beings with innate magical abilities, and the Spirits of Vengeance, the only beings capable of facing Zarathos head on. They united against him, but a Blood faction dubbed the Fallen came to worship Zarathos, strengthening the demon by channeling mankind's negative energy into him, and he briefly obtained the Medallion. The Spirits of Vengeance sacrificed themselves to seal Zarathos essence alongside theirs within the Medallion, which the Blood then shattered. To prevent the pieces ever being united, they were given to two separate human families, who were watched over by the Blood Caretaker.
2000 years ago, hearing the legends, the mage K'nutu led his starving tribe to find Zarathos' early remains, and against the chief's protest, summoned Zarathos' essences back to Earth. Though diminished because part of him remained trapped in the Medallion, Zarathos led the tribe to conquer their neighbors in return for worship and souls to consume, beginning with the protesting chief. The Cult of Zarathos built a city of Ten Thousand Souls, but the Hell-Lord Mephisto - angered that Zarathos was destroying souls that might otherwise be his and regarding Zarathos as a potential rival - sent a man, later known as Centurious, to confront Zarathos. When Zarathos tried to consume his soul. Centurious proved to be immune, his soul already claimed by Mephisto; momentary doubt amongst Zarathos' followers grew when Zarathos proved unable to defeat a manifestation of Mephisto, allowing Mephisto to claim Zarathos' soul. Over subsequent centuries Mephisto bound Zarathos to human servants, wielding his flames in Mephisto's cause, his memories wiped to make him compliant. Nearly 20 years ago the Zarathos spirit fragment within the shattered Medallion possessed Max Parrish, rescuing his sister Cammy from the ancient sorcerer Comte St. Germaine. Zarathos would have kept his host stolen body, but a youthful Johnny Storm separated Max from the Medallion. Mephisto apparently claimed the errant soul fragment, as Zarathos' essence was reportably absent from the Medallion's later users. Mephisto merged Zarathos with stunt rider Johnny Blaze, one of the Caretakers charges, transforming into the vigilante Ghost Rider. Blaze and Zarathos remained bonded for years, their level of control over their shared form varying; twice they were briefly separated, once by the mage Azaziah hoping to usurp Zarathos' power, and them by Mephisto as part of a wager with Asmodeus, but were rejoined both times. Shortly after Nightmare restored Zarathos' lost memories, Ghost Rider encountered Centurious again; when Centurious was sucked into his own Crystal of Souls, Zarathos willing followed seeking vengeances, breaking his bond with Blaze.
Reclaiming the crystal, Mephisto wagered with the Beyonder, who freed Zarathos to break Spider-Man's spirit, but Zarathos failed and was reimprisoned. Centurious was later freed, perhaps by Mephisto unknowingly carrying Zarathos' essence within him. Eventually escaping. the initially confused Zarathos joined the demon Lilith and her Lilin in seeking the Medallion pieces, battling the mystical heroes Midnight Sons, who included, Blaze, the new Ghost Rider (Daniel Ketch), and Vengeance all three were the Caretaker's charges, with the latter two wielding Medallions fragments and possessed by Spirits of Vengeance. The Sons extradimensionally banished the Lilin, but the Fallen's arrival spared Zarathos. Though Zarathos commanded his followers to convert or kill the remaining Blood, he quietly harbored doubts about repeating past glories, feeling the world offered new passions. He drained Ghost Rider's essences, but it burned him from within, and the Midnight Sons impaled him with the Blood Foundry's sword, turning him to stone again while his soul was lost between dimensions. The Sons left him in Cypress Hills Cemetery, unaware Lilith was carrying his child. Mephisto's son Blackheart later kidnapped Blaze, using him to draw Zarathos back briefly remerging them as Ghost Rider. Although that bond was seemingly broken, Blaze has since become Zarathos' host again; how this happened remains unrevealed.