Headmaster Osmond, also known as Old Osmond, leads Tristain Academy of Magic. Thirty years before the main events, an injured American soldier from the Vietnam War saved Osmond from a dragon, killing the creature with a rocket launcher later called the "Staff of Destruction." The soldier died soon after; Osmond buried him with one launcher and presented the second to the Tristain Royal Court.

A Square-class wind mage, Osmond possesses significant magical power. His familiar, a mouse named Motsognir (or Chuchu), often spies on his secretary, Longueville, specifically to see her undergarments. This habit frequently results in Longueville kicking him or confiscating his pipe. Despite his lechery and occasional feigned senility, Osmond demonstrates shrewd judgment in critical moments. He observed Louise de la Vallière's explosive failure during the Familiar Spirit Summoning Exam through his familiar.

Osmond identified Saito Hiraga's runes as belonging to Gandálfr, the legendary familiar of the Void element. Recognizing the sensitivity of this discovery, he ordered Colbert to keep it secret. When Fouquet the Crumbling Earth stole the Staff of Destruction, Osmond tasked Louise, Kirche, and Tabitha with retrieving it, assigning Longueville as their guide – unaware Longueville was Fouquet in disguise. After the staff's recovery and Fouquet's arrest, Osmond explained the weapon's origins to Saito, recounting the incident with the American soldier.

In the OVA, Osmond collaborated with male students to trick female students into wearing swimsuits from Saito's world under the guise of a water spirit ritual. His administrative responsibilities included safeguarding academy treasures and liaising with royal envoys, like Count Mott, regarding security threats.