Roux de Val Perilleus
A traitorous relative of Arthur who, hearing that Arthur was away on adventures, invaded the land of Cardigan and captured Arthur’s castle at Disnadaron (Dinasdaron).
Arthur eventually rallied his forces and marched on the city, and the Red Knight fled, intending to fortify himself in his impregnable castle in the Perilous Valley. He was intercepted along the way by Gawain and Meriadeuc. Meriadeuc defeated him and forced him to surrender to Arthur.
Meriadeuc or Le Chevalier aux Deux Épées | c. 1225-1250