Poem 31 of the Black Book of Carmarthen, a mid-13th century manuscript, is known from its first line as Pa gur yv y porthaur?
[4] Pa gur is notable for being one of the earliest vernacular Arthurian works, and for alluding to several early adventures of Arthur which are now lost.
Glewlwyd Gafaelfawr duly identifies himself and returns the question, upon which Arthur names himself and says his party consists of Cai the Fair and "the best men in the world".
The subject now turns to Arthur himself, who is said to have fought against a witch in the hall of Afarnach, against a certain Pen Palach in the dwellings of Disethach, and against dog-heads at the mount of Edinburgh.
Not only is his vengeance heavy and his anger bitter, but When he drank from a hornhe would drink like four.So mighty a warrior is Cai that his death can only be contrived by God himself.
His companions – including Cai and Bedwyr, both important figures in later Arthurian legend – each have their own qualities which they can bring to any encounter, but Arthur is a fighter in his own right, not just a commander.
[22][23] It has been suggested that Arthur himself has supernatural powers in the poem, specifically the ability to make himself and his men invisible, though this interpretation rests on a contested translation of a difficult line.
One general similarity lies in the use both works make of allusion to a string of stories featuring Arthur and his men,[26] but there is also a more specific one.
[34] The fight at Tryfrwyd in Pa gur seems to be identical with the bellum Tribruit, listed by the Historia Brittonum as one of Arthur's twelve battles.
[35][36] But whereas Historia Brittonum treats the battle as historical, in Pa gur it is entirely mythical, being fought against the werewolf Garwlwyd and an army of dog-headed monsters.