Mordred is a character from Arthurian legend. In some of the legends, he betrayed Arthur and killed him. He is said to be Arthur's son by Morgaine (also called Morgan or Morgana), his half-sister. Mordred was born at Caerlon. Mordred was also said to have been killed by Arthur after he stole Excalibur from him. He was killed while Arthur was fatally wounded. This part also occurs in the very famous movie about King Arthur.