Marte
An evil castle.
Its king was Perceval’s maternal uncle, but the king’s family disavowed him because of his evil ways. The king attacked the Castle of the Galleys and the Grail Castle. The latter belonged to his own brother, the Fisher King.
The king fled from Perceval at the Castle of the Galleys. He seized the Grail Castle upon the Fisher King’s death, but Perceval re-conquered it. Beholding his own defeat, the King of the Castle Mortal threw himself off the Grail Castle’s battlements to his death.
Source
Perlesvaus | Early 13th century