Lady of the Lake

Origin
The Lancelot-Grail Cycle provides a backstory for the Lady of the Lake, "Viviane", in the prose Merlin section, which takes place before the Lancelot Proper, though it was written later. There, Viviane learns her magic from Merlin, who becomes enamored of her. She refuses to give him her love until he has taught her all his secrets, after which she uses her power to trap him either in the trunk of a tree or beneath a stone, depending on the story and author. Regardless of the specific version, Merlin is unable to counteract Viviane because of his foresight; because of such an ability and the "truth" it holds, he decides to do nothing for his situation other than to continue to teach her his secrets until she takes the opportunity to entrap and entomb him in a tree, a stone or a cave.

The Post-Vulgate Cycles second Lady of the Lake is called "Niniane'", and her story is nearly identical to the previous one, though it adds her bestowal of Excalibur to Arthur. Sir Thomas Malory also uses both Ladies of the Lake in his Le Morte d'Arthur; he leaves the first one unnamed and calls the second one Nimue. Malory's original Lady is presented as an early benefactor of King Arthur who grants him Excalibur when his original sword is damaged. She is later beheaded by Sir Balin as a result of a kin feud between them (she blames him for the death of her brother and he blames her for the death of his mother) and a dispute over an enchanted sword.

Both characters appear in many other episodes of Malory's work. Each time the Lady reappears, it is always at a pivotal moment of the episode, establishing the importance of her character within Arthurian literature, especially Le Morte d'Arthur. In that work, she transcends any notoriety attached to her character by aiding Arthur and other knights to succeed in their endeavors. After enchanting Merlin, Malory's Nimue replaces him as Arthur's adviser. She becomes the lover and eventual wife of Sir Pelleas and mother to his son, Guivret. After the Battle of Camlann, she reclaims Excalibur when it is thrown into the lake by Sir Bedivere. Nimue is one of the four queens who bear the wounded Arthur away to Avalon, a setting tied to the Lady of the Lake in some literary traditions.