Vivienne

Vivienne Le Fay was the wife of Gorlois, with whom it is possible she had a daughter called Morgause, although this is extremely unlikely, as Gaius described Morgause as Morgana's half-sister, at a time when Morgana was thought to be Gorlois' daughter.

Vivienne, High Priestess of the Old Religion and of the Triple Goddess, had forged this bracelet on the Isle of the Blessed.

When Gorlois was away at battle, Vivienne had a brief affair with her brother-in-law, Uther Pendragon, and conceived Morgana. She had Gorlois believe that he was the father of her second child. It is likely that he never found out about his wife's affair. Vivienne was most likely a witch and had passed on her magical powers to her two daughters.

Despite being magical, Uther likely chose not to have her executed because she was the sister of his wife, Ygraine. Though he saved Morgana, because she was his daughter, Uther also ordered for Vivienne's eldest daughter to be drowned, but Morgause escaped because Gaius smuggled her from Camelot, and Morgause now wants to avenge her family. She owned a magical bracelet that her eldest daughter inherited from her, which Morgause then passed on to her younger sister, Morgana.

It is unknown what happened to her after Morgana's birth, as Morgana has never mentioned her, she has mentioned only Gorlois, which is implied that until she went to live with Uther, she was raised by Gorlois alone. It is believed that she died after Morgana's birth, but no character has mentioned that she is actually dead.

Vivienne is the sister of Ygraine, Tristan and Agravaine (citation needed) and likely was a lady-in-waiting to Ygraine when Ygraine was Queen.

In the Legend
Vivienne, spelled Viviene, is one of the names for the Lady of the Lake. Also known as Nimueh or Nineve, she is the one who gives Excalibur to Arthur, steals the infant Lancelot and traps Merlin in a stone.