Lucifer exists as a fallen angel within the Saint Beast universe. Once the right-hand angel to Zeus, the deity ruling Heaven, his relationship with Zeus soured, leading to his banishment for reasons not fully detailed in the anime.

Before his fall, Lucifer interacted with younger angels like Judas and Luca. Flashbacks, including one recounted by Judas, portray him as a kind and respected figure admired by the younger generation. A significant shift in his motivations and allegiance occurred. The OVA *Ikusen no Hiru to Yoru Hen* hints at deeper complexities in Heaven's hierarchy, suggesting Lucifer's possible involvement with Zeus in a contentious act, such as overthrowing Cronus, Zeus's predecessor. This act, and potential subsequent disagreements, contributed to his casting out.

Following his banishment, Lucifer's demeanor transformed. He reemerges briefly in the main timeline with an altered attitude and agenda. He directly approaches Judas, advocating rebellion against Zeus and proposing the creation of a new paradise in Hell, separate from Zeus's dominion. Judas refuses this recruitment attempt, though Lucifer expresses confidence Judas will eventually reconsider. Lucifer's physical appearance is consistently noted as having long black hair and wearing black angelic garments.

His influence extends beyond direct appearances. He is frequently mentioned alongside Gabriel as one of the primary fallen angels residing in Hell, representing an alternative to Zeus's rule. A significant rumor, explored in drama CDs but not confirmed within the anime narratives, suggests Lucifer is the angelic father of the half-angel, half-human brothers Kira and Maya. Kira's knowledge of a shameful angelic father figure lends some credence to this possibility within the broader lore. Lucifer does not appear again after confronting Judas, leaving his ultimate fate and the full extent of his actions in Hell unresolved within the animated adaptations.