Guidam, Guidans, Guidant
A lord who stole the land of Valingues from his sister-in-law, murdering her fiancée.
Gaheris (Gawain’s brother) championed the maiden against Guidan in a duel at Roestoc. When it became apparent that Guidan would lose the combat, he jumped into a river and drowned.
Source
Vulgate Lancelot | 1215-1230