Fimbeus
The lord of Sardin in the country of Angiez.
He was married to a goddess named Giramphiel, who had Lady Fortune supply him with a special belt. This belt, garnished with enchanted stones, made its wearer not only strong and brave, but also handsome and charming. During a visit to Arthur’s court, Fimbeus lent the belt to Queen Guenevere, who coveted it so much that she ordered Gawaine to fight Fimbeus for it. Gawaine reluctantly complied, and won.
Giramphiel later managed to steal from Gawaine the stone that was the source of the belt’s power. She returned it to Fimbeus. Gawaine embarked on a quest to recover the victory stone for Arthur’s court, the culmination of which brought him to Sardin, where he again defeated Fimbeus, recaptured the stone, and obtained Fimbeus’s fealty.
Source
Diu Crône | Heinrich von dem Türlin, c. 1230