Roswaal L. Mathers serves as a schoolteacher in an alternate world setting. His striking appearance features heterochromia—a yellow left eye and blue right eye—accompanied by long indigo hair and distinctive lavender face makeup. He favors flamboyant clothing resembling a jester's attire, complete with purple and black garments, a cape, and boots. Without the makeup, his complexion appears notably pale and his expression gentler. He stands 186 centimeters tall. The body currently inhabited belongs to the twelfth incarnation of a soul originally named Altair Mathers, later known as Roswaal A. Mathers. Born over 400 years prior into the noble Mathers family, he suffered debilitating pain from uncontrolled magical energy until the Witch of Greed, Echidna, saved him by repairing his magic gate. She became his mentor, inspiring obsessive devotion. Following Echidna's death, he resolved to resurrect her, initiating a centuries-long plan involving body possession. Upon each death, his soul transfers into a direct descendant, adopting their body while retaining his identity and memories. The current host body is approximately 20 years old, though the soul within exceeds 400 years in age. In his original era, Hector, the Devil of Melancholy, attacked Echidna. Roswaal fought Hector but suffered defeat, resulting in psychological trauma that led him to permanently adopt Hector's speech patterns and clown-like makeup. Echidna later perished in a conflict with the Holy Dragon Volcanica. Roswaal dedicated subsequent centuries to mastering magic and devising resurrection methods, relying on a copy of Echidna's Tome of Wisdom that predicted future events to guide his actions. To achieve his goals across generations, he manipulated political events and orchestrated tragedies, including permitting the Witch Cult's attack on an Oni village to eliminate all but the twin sisters Ram and Rem, whom he adopted for their potential. As lord of Roswaal Manor and Margrave of Lugunica's western territories, he sponsored Emilia's candidacy in the royal selection while secretly intending to use her, Subaru Natsuki, and Ram to kill the Divine Dragon and revive Echidna. He recognized Subaru's ability to return after death and engineered crises to exploit it. During Arc 4, his Gospel was destroyed and he lost a bet against Subaru concerning Sanctuary's liberation. This defeat forced him to swear an Oath Bound Curse preventing harm to Emilia's camp under penalty of soul destruction. Consequently, he shifted to genuine support for Emilia while maintaining his ultimate ambition. Post-bet, he displayed increased leniency toward allies like Otto Suwen and Garfiel, even offering combat guidance. Roswaal's magical capabilities rank him as Lugunica's strongest mage, his power equivalent to an entire army. He wields all six elemental magics except healing, attributing this limitation to insufficient regard for life. Specialized spells include fire projectiles ("Goa," "Ul Goa"), inferno creation ("Al Goa"), weather alteration ("Altemillion"), and spectral flames. He employs flight magic and martial arts. His yellow left eye can neutralize enemy spells. A Divine Protection of Sorcery, referenced in some sources but considered non-canonical in others, enhances his elemental affinity. Within the school environment, he enforces discipline through detentions and academic oversight, exemplified by assigning Kazuma Sato to the disciplinary committee after wine theft incidents and expelling Aqua for cheating. He accommodates unique abilities like Megumin's explosion magic during field demonstrations. Relationships mirror original dynamics: he retains mutual respect with Beatrice based on shared history with Echidna, maintains a confidant role with Ram—accepting her Valentine's chocolate—and observes Subaru's actions while offering veiled advice about caution. He opposes Albedo's hostility toward other students and declines social interactions with entities like Kyouhukou.