Little is known of his reign, but it ended when, as described in the
Annales Cambriae, the sons of
Eliffer,
Peredur and
Gwrgi, the joint kings of
Efrog, killed him at the
Battle of Arfderydd in 573. It is possible he was succeeded by one of his brothers. This was one of many battles fought between Brythonic kings who led the various fractured successor states that took over the Roman province of
Brittania following the Roman withdrawal. In Welsh mythology, he is the owner of one of the
Thirteen Treasures of the Island of Britain: a magical chessboard / gwyddbwyll board. If the pieces were set, they would play by themselves. The board was of gold, and the men of silver. Although Gwenddoleu plays no part in
Arthurian legend, his court adviser
Myrddin formed part of the basis for the later Arthurian legends concerning the wizard
Merlin. In
Geoffrey of Monmouth's
Vita Merlini, Myrddin (Merlinus) is said to have been driven mad with grief following the death of Gwenddoleu and to have fled into the Caledonian forest. The memory of both Gwenddoleu and Myrddin was preserved in
Welsh literature. ==References==