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 his half-sister Morgaine (also called Morgan or Morgana). 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. His name comes from old Welsh. He was not a knight of the round table.