Duel between Merlin and Nimueh

A magical duel between Merlin and Nimueh occured in the Isle of the Blessed. When Arthur Pendragon got bitten by a Questing Beast, Merlin was forced to go to the Isle of the Blessed where he met Nimueh again. Merlin offered to give his life to save Arthur's, Nimueh instead took the life of his mother Hunith, while Arthur was saved. When this happened Gaius visited Nimueh and gave his life, saving Hunith.

Merlin rode to the Isle of the Blessed in order to save Gaius, but he arrived too late. Merlin framed Nimueh to have organized all of this to take her revenge on Arthur, Gaius and Camelot. She told the young warlock that they were too valuable to each other to be enemies, but when she said she would be the one to make Arthur king, Merlin attacked her with magic and cast a blast of magical energy stretching out his hand. Anyway Nimueh stopped his spell easily, because she was a powerful High Priestess of the Old Religion. Nimueh then started sending him fire balls and she apparently emerged victorious when Merlin seemed to be killed but he later recovered. The duel ended when Merlin struck his opponent with a lightning, revealing that he had mastered the Power over Life and Death. By doing this, he sacrificed Nimueh's life to the Old Religion in order to save Gaius' (Le Morte d'Arthur).