Sir Gahalantine was a relative of Sir Lancelot and Knight of the Round Table. The two chose opposing sides at the tournament between King Bagdemagus of Gore and the King of North Wales. Sir Gahalantine fought for the Welshman, but was sorely beat by his cousin. Gahalantine supported Sir Lancelot during his break with King Arthur and helped him rescue Queen Guinevere from the stake. In return, Lancelot made him Duke of Auvergne. After Arthur's death, Gahalantine joined Lancelot and his companions in their hermitage. He returned home after Lancelot's own demise.