Zarathos fought the ancient Spirits of Vengeance and corrupted a number of their overseers, the Blood into his "Fallen. Although he promised them increased power, in actuality Zarathos was using their powers to further augment himself.
After gaining power and worshipers, Zarathos then challenged Mephisto for ownership of his realm. Mephisto tricked Zarathos by having Centurious. Centurious' lack of a soul rendered him immune to many of Zarathos' power. With his followers abandoning him, Zarathos was easily defeated.
On occasion, Mephisto would forcibly bond Zarathos to mortals as a mockery of the Spirits of Vengeance. On one such occasion, he bonded Zarathos to carnival stunt cyclist Johnny Blaze, transforming him into the Ghost Rider. After serving as the Ghost Rider for many years, Zarathos was contained inside of mystic relic known as the Soul Chamber. He was briefly released by the Beyonder in attempt to tempt the latter into killing the Kingpin. The soul chamber was later seen in Mephisto's possession during a visit by Loki.
However, Zarathos appeared again, having hid inside Centurious until freed by Lilith. Joining with Lilith, they planned to take over Earth and were opposed by the Midnight Sons. The Fallen also returned to assist Zarathos. However, the destruction of the Fallen, his absorption of Ghost Rider and the powerful weapon, Justiciar all led to Zarathos' destruction. He remained a lifeless statue in the Cypress Hills Cemetery, until recently when he reconstituted himself within Johnny Blaze[1]. Lilith appeared, carrying his child, saying that she would avenge him.
Zarathos possessed incredible elemental powers further augmented by leeching power from the Fallen. He was also capable of using hellfire, primarily when hosted by Blaze.