Nimuë is one of the women identified as the Lady of the Lake, who give Arthur the sword Excalibur. And also give Gawain the sword Galatine. She is also one of the women who come to the battlefield of Camlann to take Arthur to Avalon.
Sometimes, in later stories, she is depicted as Merlin’s apprentice with whom he is hopelessly in love. Often, she is the one who enchants Merlin, sealing him up in a cave or a tree, whereupon she takes his place as advisor to Arthur.
I’ve already written the first scenes with my version of Nimuë.
Morgana is also an enchantress, though generally a benevolent one, acting as a magical protector to Arthur. Usually, she is the youngest daughter of Igraine and Gorlois, making her Arthur’s half-sister.
She is especially associated with Avalon (or the Isle of Apples) where her chief role is as a healer. Avalon was associated with mystical practices early on. One possible location for Avalon is Glastonbury Tor—a conical hill rising a bit over 500 feet above the Someset levels. It would have been surrounded by a marsh, making it sort of an island. It is also the location in which Excalibur was said to have been forged.
Morgana is one of the women who come to take Arthur from Camlann to Avalon, where he will be healed, perhaps to return.
Possibly because of her association with Avalon, she is also sometimes considered a Lady of the Lake.
In some versions, she is also the reluctant wife of King Urien of Rheged, and therefore the mother of Owain (Yvain) and a daughter Morfydd, who was Owain’s twin sister.
In Geoffrey of Monmouth’s version, she is a shapeshifter who can fly on strange wings and uses her powers only for good. Hmm, I just might make use of that.