A British fortress in which Peredur had an adventure. Peredur was lead to the fortress by one of his cousins, who was in the guise of a hag. Upon reaching the fortress, Peredur found it deserted except for an enchanted gwyddbwyll set (a chess-like game) which he threw into a river after it continually defeated him.
Peredur’s cousin showed up again in various disguises and eventually pointed him to the Hags of Gloucester, whom Peredur was fated to destroy in revenge for the death of another cousin. A similar event takes place in the Didot-Perceval at Chessboard Castle.
Source
Peredur | 13th century