A castle on the island of Perfida, visited by Tristan and a maiden named Tessina during Tristan’s adventures in Logres.
Tristan was imprisoned and forced to fight the castle’s champion, Lamorat. Lamorat had assumed the position after slaying the previous champion. By custom of the castle, one of the two knights would have to die in the combat, but Tristan feigned death and they were both able to escape later.
Tessina was beheaded because her beauty did not match that of Medeas, the castle’s pagan queen.
Source
La Tavola Ritonda | 1325–1350