A castle ruled by King Agravadain the Black, who assisted Arthur in the Saxon Wars. It was visited by Merlin and Ban, the latter of whom, because of an enchantment cast by Merlin, slept with Agravadain’s daughter, begetting Hector.
During Hector’s adventures, he was imprisoned at the Castle of the Fens after he slew Mataliz, the lord’s son, which means either that the castle had a change of ownership, or that it occurred at a different castle of the same name. Hector won his freedom by championing the lord’s niece, Elaine the Peerless, against her husband.
See also
Saxons | The Legend of King Arthur
Sources
Vulgate Merlin | 1220-1235
Vulgate Lancelot | 1215-1230