Oz is a wizard from the Northern Country, summoned as a Sage's Wizard for the Central Country. Universally acknowledged as the world's most powerful wizard, his fearsome reputation inspires dread in both humans and wizards, painting him as cruel and heartless. He shuns public appearances and resists any meddling in his affairs.

Physically, Oz is exceptionally tall. He has navy blue hair tied in a high ponytail reaching his knees and striking red eyes. His attire favors dark colors—red, maroon, gold, and black—often comprising a long coat reminiscent of a royal military uniform, a vest, a buttoned shirt, and a red ruffled ribbon fastened with a yellow jewel. His wizard crest is positioned under his collarbone, with sources differing on whether it is left or right.

His history spans more than 2000 years. Abandoned as an infant for being a wizard, he initially behaved like a wild beast, consuming mana stones for survival, lacking speech or comprehension. The twins Snow and White, along with Figaro, took him in and educated him. Figaro once proposed turning the young Oz to stone preemptively but instead aided in raising him. As Oz matured, his overwhelming power became a burden, attracting relentless demands for protection or assassination. Seeking freedom through tyranny, he conquered half the world with Figaro's shadowy support. Mid-conquest, he realized this path only forged more unwanted bonds and abruptly retired to a Northern castle, leaving behind a monstrous legend.

Centuries later, Oz discovered Arthur Granvelle, the four-year-old prince of the Central Country, abandoned in the Northern snow. Initially claiming he took Arthur in to eventually consume his mana stone, Oz instead raised him as a foster parent for nine years. This experience profoundly changed him, uncovering latent kindness and reshaping his worldview. He learned alongside Arthur, exploring simple wonders like why the sky is blue or fish cannot fly. When the Central Country reclaimed Arthur, Oz experienced unprecedented grief, unleashing years-long blizzards across the North. He repeatedly burned and rebuilt Arthur's room in despair, avoiding contact until learning Arthur was summoned as a Sage's Wizard. To protect Arthur from threats—especially Northern wizards—Oz joined the Sage's Manor under its rules.

Oz's personality blends calm detachment with social awkwardness. He speaks slowly and literally, frustrating quicker minds like Riquet. Though historically intimidating, his affection for Arthur softened him, allowing rare smiles when speaking of his foster son. He shows humility regarding his power, acknowledging it shouldn't be abused, though Northern provocations can still ignite his wrath. Younger wizards, unaware of his legend, treat him casually, contrasting with older wizards' wariness.

A key vulnerability is his "Calamity Injury": a curse forcing him into immediate sleep at night, nullifying his magic. Antagonists like Obsius exploited this weakness by timing rituals accordingly. Prophecies revealed by Snow and White indicated Oz altered fate to replace Arthur as Central's summoned wizard, averting Arthur's prophesied death against the Great Calamity. When confronted about his nighttime vulnerability, Oz reacted furiously, rejecting reliance on Northern wizards for protection.

Currently, Arthur, Cain, and Riquet serve as his moral anchors, with Arthur remaining his deepest emotional connection. Oz mentors Cain in magic and maintains tense rivalries with Northern wizards like Mithra, who seek to dethrone him as the strongest. Despite his aloof exterior, he demonstrates care for younger wizards, intervening in crises—such as neutralizing Aureolin during an attack at Granvelle Castle—and collaborating with Figaro to investigate threats linked to his magic.