Osgar was a sorcerer who had been summoned by the Triple Goddess and the court of The Disir to deliver a runemark to Arthur Pendragon. He used his magic to kill Sir Ranulf and to defeat other Knights of Camelot in order to gain the King's attention. Arthur and his men, including Mordred and Merlin, set out to find the warlock; when Gwaine and Elyan tried to capture him, he disarmed them with a non-verbal spell. Gwaine, however, was quick enough to stab him in the stomach, but Osgar used a stunning spell to knock them out. He then approached Arthur quickly before his death and delivered the judgement of the Goddess, speaking his last words (The Disir).