The Battle of Arfderydd (also know as Arderydd) is fought in 573 according to the Annales Cambriae.
The opposing armies are variously given in a number of Old Welsh sources, perhaps suggesting a number of allied armies were involved.
The main adversaries appear to have been Gwenddoleu ap Ceidio and either the princely brothers, Peredur and Gwrgi, or King Riderch Hael of Strathclyde.
Gwenddoleu is defeated, and his forces slaughtered.
His bard, Lailoken, said to be named also Myrddin Wyllt, goes mad and runs into the forest.
He is probably the original of the Arthurian character, Merlin, though this historical figure has no connection to King Arthur. (In a late fifteenth century manuscript, a story called 'Lailoken and Kentigern' places the battle on the plain between Liddel and Carwannok. This is believed to be at Arthuret, near Longtown, in Cumberland, now Cumbria).
Welsh tradition regards Riderch, or Rhydderch, as one of the northern British kings who fought against the early Anglo-Saxon realm of Bernicia.
