At the time of Arthur’s war with the eleven rebel rulers at the outset of his reign, Rience was at war with Leodegrance. He had a cloak made from the beards of eleven kings and sent to Arthur demanding his for the twelfth. War ensued, and Balin and Balan captured Rience and brought him captive to Arthur.
Modern Welsh tradition describes Rience as a robber whom Arthur slew and buried in the vicinity of Llannwchllyn.
He is presumably identical with Rhitta, Ricca or Ritho, a giant associated in Welsh folklore with Snowdonia, whom Arthur killed. The Livre d’Artus describes him as a Saxon. Spenser made him the father of Britomart.