Mordred

Mordred or Modred (/ˈmoʊdrɛd/; Welsh: Medraut, Medrod, etc.) is a character in the Arthurian legend, known as a notorious traitor who fought King Arthur at the Battle of Camlann, where he was killed and Arthur fatally wounded. Tradition varies on his relationship to Arthur, but he is best known today as Arthur's illegitimate son by his half-sister Morgause. In earlier literature, he was considered the legitimate son of Morgause, also known as Anna, with her husband King Lot of Orkney. His brothers or half-brothers are Gawain, Agravain, Gaheris, and Gareth. The name (from either Old Welsh Medraut, Cornish Modred, or Old Breton Modrot) is ultimately derived from Latin Moderātus.

Read more about Mordred:  Mordred in Arthurian Legend, Mordred's Background, Mordred in Later Works