A knight whose brother, Gallinor, was imprisoned by Baudon of Avarlan. Gallin challenged Baudon for Gallinor’s freedom, but was badly wounded before the duel could be fought.
Coming upon a party of Arthur’s knights, he related his story, and Gaheris agreed to fight against Baudon in Gallin’s stead. Gaheris was victorious, and Gallinor was freed.
Source
Post-Vulgate Suite du Merlin | 1230-1240