Arthur was betrayed by Sir Lancelot, who had a love affair with the king’s wife, Guinevere, causing a terrible struggle between Arthur and his old associate, Lancelot. Arthur was said to have been betrayed and killed by his son (or nephew) Mordred (Modred) in the war. But another tradition has it that he was not killed but was taken away by fairy queens, perhaps one of them his half-sister Morgan Le Fay, to the mysterious island of Avalon—the Isle of Women in the old Celtic tradition—from which, one day, he would return to Britain to rule.