|"Sir Mordred" (1902) by H. J. Ford|
In the 2008 Merlin episode "The Beginning of the End", he plays a young druid boy who is hunted by Uther Pendragon who wants to sentence him to death because he feels threatened by the boy's magic. Despite the Great Dragon's advice and the warning that Arthur cannot survive if the boy does, Merlin, with the help of Morgana, helps the boy escape Camelot and returns him to the druids. When they are about to disappear into the forest Arthur asks him for his name. The druid boy identifies himself as Mordred.
Great Mordred clip from Merlin, showing off a couple of his powers, but not nearly touching upon the extent of them. (Some violence, maybe PG-13):