The wife of Caradoc Briefbras and a lady at Arthur's court in Welsh tradition. She had three treasures: a mantle, a cup and a carving knife.
She possessed an enchanted mantle which, when worn by a woman, would tell if she was faithful or adulterous by appearing, respectively, a perfect fit or too short. Such mantles are used in chastity tests throughout Arthurian romance.
Chrétien de Troyes calls her Guignier in Perceval.
Thirteen Treasures of Britain | The Legend of King Arthur