This castle may have been on the other side of the waste forest near Carteloise Castle.
The “Castle of the Leprous Lady” should not be far from Carteloise Castle and Carteloise Forest. It must be near a river or harbor, since Galahad and his companions put Amide’s body into a barge and let it drift to Sarras to meet them there. If Carteloise is put on the north shore of Solway Firth, the Leprous Lady’s castle might be located at, say, Annan.
See also
Aspetta Ventura | The Legend of King Arthur
Dindraine | The Legend of King Arthur
Leprous Lady | The Legend of King Arthur