Lucius Oriflamme, known as Luca, is the hereditary Grand Duke of vampire society, a position granting significant influence despite his pre-adolescent age. His appearance reflects his youth: a round, childlike face, large upturned green eyes, long eyelashes, and short reddish-brown hair with cowlicks. He typically wears formal attire: a green, silver-detailed mantle like a houppelande, short black pants, a white shirt, white socks, black shoes, and a detailed green hat. Luca's personality balances outward calmness, responsibility, and maturity with underlying naivety and emotional vulnerability. He often suppresses childish instincts due to his status, exhibiting nervous habits like clutching his clothes, bag, or hands when distressed. He displays intense protectiveness—especially towards his chevalier, Jeanne—and explosive aggression when those he cares for are threatened. This fierce loyalty extends to his older brother, Loki Oriflamme, whom he calls his "precious person"; Loki's status as a curse-bearer motivates Luca's quest for the Book of Vanitas. His story starts in the Parisian Excursion Arc, confronting Vanitas and Noé Archiviste to demand the Book for Loki's cure. After Vanitas refuses and insults him, Luca orders Jeanne to retrieve the Book by force. When Vanitas forcibly kisses Jeanne, Luca unleashes uncontrolled pyrokinesis—body-generated flames—before retreating with her. During the Bal Masqué Arc, Luca apologizes to Noé for his aggression, acknowledging his emotional immaturity. He witnesses Charlatan's curse-bearers attack the ball and Noé's trauma. Later, at a café, he demands Vanitas apologize for kissing Jeanne, showing deep concern for her. His relief upon learning the kiss was non-consensual but not romantic underscores his protectiveness. In the Beast of Gévaudan Arc, Luca asserts his authority at a senate meeting. When a senator proposes executing Jeanne for her actions, Luca interrupts, declaring he will not allow his chevalier to be harmed, securing her safety under his protection. The Amusement Park Arc highlights his vigilance over Jeanne. He becomes furious learning she spent a night alone with Vanitas. When Jeanne confesses romantic feelings for Vanitas, Luca panics and takes her to Dominique de Sade for counsel. Later, noticing Dominique's absence, he tasks Jeanne with investigating. Luca's key relationships define him. He trusts his adoptive uncle, August Ruthven, as a parental figure but resists Ruthven's overt affection to maintain dignity. His bond with Loki is his primary emotional anchor; he seeks physical comfort from Loki during terror, like sensing Queen Faustina's presence, displaying vulnerability unlike with others. His devotion to Jeanne manifests as fierce loyalty, prioritizing her safety over politics. His interactions with Noé evolve from hostility to mutual respect, culminating in a friendly outing where Luca expresses his wish to mature quickly. As a high-ranking vampire, Luca possesses enhanced speed, strength, and endurance. His notable ability is pyrokinesis, generating explosive flames, though he struggles to control it, especially during extreme emotional outbursts.