Guin Godybrion, Gwyn Godybrion, Gwynn Gotyuron
Originally a Celtic god, the son of Nodens; in later belief, a warrior.
He and his followers fought the followers of Gwythr, son of Greidawl, for the maiden Creiddyled. To stop the general bloodshed, Arthur made an agreement for the pair of them to fight each other at May Kalends (or May Day) until Doomsday. The winner then would obtain the hand of Creiddyled. Arthur made Gwyn ruler of the demons of Annwfn to stop them destroying humanity.
Together with Mabon and Kysteint mab Banon he was a ‘sage’ and warrior of Arthur’s retinue in Pa gur.
Sources
Culhwch and Olwen | Late 11th century
”Dialogue of Arthur and Gwenhwyfar” | 16th century