Morgan le Fay is a popular figure in many Arthurian legends: she's a fairy, half-sister of King Arthur.
Daughter of Igraine and Gerlois, the Duke of Cornwall, she appears in Arthurian romances under many different names: Fata Morgana, Morgana le Fay, Mordron, sometimes identified with Argante, the "Elven Queen of Avalon" or "Queen of the Lake of Avalon".
Generally described as having magic power of healing, which she learned from Merlin.
Morgan le Fay inspired the adventures of Sir Gawain and the Green Knight. She was an enemy of Queen Guinevere, the wife of King Arthur.