Nimue is the name given to various incarnations of a witch/sorceress in many movies and TV shows (most recently, the Blood Queen in Hellboy (2019). The mythology on which the characters are based indicate she was schooled in magic by Merlin before, ultimately, binding and imprisoning him forever. Other myths have her becoming the 'Lady of the Lake' who raised Sir Lancelot, returning Excalibur to King Arthur and, eventually, taking his body to the realm of Avalon. (The two variations, however, seldom exist in the same telling of the story.)