Lady of the Lake
The Lady of the Lake is a mythological person from Arthurian fables. She is said to have given King Arthur the legendary sword Excalibur. Which Sir Girflet would return to her when though the sword back into the Enchanted Lake.
The Lady of the Lake is also said to have, at some stage entombed Merlin in a tree, stone or a cave after he taught her all of his secrets. He is beleived to have known it was going to happen as he was gifted with foresight. But he believed you could not change the future and allowed it to happen.
It is now known that the Lady of the Lake was a Mage called Vapist.