I found some of the text about King Arthur fighting werewolves in his tenth battle. Here it is, from the Welsh peom Pa Gur?:
Though Arthur laughed
he caused her blood to flow
in Afarnach’s hall,
fighting with a witch.
He pierced Cudgel’s Head
in the dwellings of Disethach.
On the mountain of Edinburgh
he fought with dogheads.
By the hundred they fell;
they fell by the hundred
before Bedwyr the Perfect
This is of extra interest to me because Morgana La Fey plays a central part in my series, and she is involved in inciting a werewolf against Arthur in the third book.
And so here, in this ancient poem, we have Arthur fighting a witch (Morgana?) at the same time he is fighting dog-heads. Fascinating. Whoever Cudgel is, I don’t know, but that is of interest to me as well.
The final conflict mentioned by the poem (lines 81-90) is a battle against lleuon [lions], wild-cats and the monstrous sea-cat Cath Paluc [Clawing Cat, later Palug’s Cat] attributed to Cai.
In other sources this features Arthur rather than Cai and it seems probable that all the sources are recounting a generally Arthurian battle, with Cai simply made prominent in Pa gur?’s telling and Arthur elsewhere.
This might well apply to all the battles referred to in the poem and it is most interesting that the Arthurian battle against were-wolves at Traeth Tryfrwyd, mentioned in Pa gur? (lines 19-22, 48-51) as involving both Bedwyr and the sea-god Manawydan son of Llyr, is included in Historia Brittonum chapter 56 as Arthur’s tenth battle