Rhydderch figures in traditional tales, and there are references to him in the Merlin poems (Black Book of Carmarthen, 49. 16, 50. 3, 52. 11, 56. 16, 57. 16). He is also referred to as the victor in the battle of Arfderydd, which was fought, according to Harl. MS. 3859 (Cymm., ix, 155) in 573. In the triads he is named as one of the ‘three liberal ones of the Island of Britain’ (Myv. Arch., 389), his court is said to have been devastated by Aidan, king of the Scots, 574-606 (ibid., 391), and ‘Drudlwyd’ is given as the name of his steed (Black Book of Carmarthen, 28. 5). According to the Black Book of Carmarthen, 64. 8-9, he was buried at Aber-erch; but this must be a late saga tradition.