Houou no Luca, one of the Six Saint Beasts, began as a high-ranking angel before his fall. His appearance features pale skin and medium-length silver-white hair tied back with black wrapping. A turban conceals a seal on his forehead, a memory-restricting tattoo placed to block recollection of his true origins. He wears a sleeveless, dark blue-green qipao with white linings, silver chokers, a studded silver belt, black pants, and tight black arm warmers reaching his wrists. Four silver bangles adorn his left wrist, and his wings are bluish-white.

Luca can fly with his wings, a trait shared only with Suzaku no Rei. When becoming a Saint Beast, Zeus granted him the additional power to read minds through his fingertips, stemming from Luca's wish expressed a day before the trials to understand Rei more deeply. He is also a proficient combatant.

Born from Zeus and a mortal woman, Luca was raised believing he was an ordinary angel, his memory seal ensuring this false identity. He initially respected Zeus as the creator and father of all angels, but this respect eroded over time. Luca ultimately joined Kirin no Judas's rebellion against Heaven. After its failure, he was cast into Hell with Judas, his feelings hardening into hatred for Zeus. In Hell, he and Judas began plotting another rebellion to overthrow Heaven and establish Hell as the true paradise.

Quiet and observant, Luca often avoids uncomfortable subjects, changing the topic even when others dwell on them, as when the Saint Beasts first discussed treason. Beneath this calm exterior lies a vengeful nature, especially after the failed rebellion.

His relationships are complex:
* He shares a long-standing, close friendship and confidant role with Judas, remaining loyal to Judas's vision of reforming Heaven. Their alliance continues in Hell.
* He maintains a protective and intimate bond with Rei, who approached him first, forging an inseparable connection. Their relationship status post-rebellion is ambiguous, though mutual care persists.
* He is close friends with fellow Saint Beasts Goh, Shin, and Gai, as well as Maya and Kira. Kira respects and follows Luca's advice due to this understanding.
* He exhibits no negative feelings toward Pandora or Cassandra, though Pandora views the Saint Beasts as rivals for Zeus's attention, and Cassandra displays passive-aggressive behavior, leaving Luca confused.
* He is aware of Shiva's feelings toward Judas but maintains civility. He has no direct interactions with Kamui or Takeru.

Luca's story arc traces his transition from respected Saint Beast to vengeful fallen angel, driven by betrayal and the revelation of his hidden heritage. It centers on his shifting loyalty, the exposure of his sealed past, and his commitment to overthrowing the heavenly order alongside Judas.