Roche aux Pucelles
A high rock on which Merlin imprisoned a lady and her many sisters, after the lady tried to kill Merlin by sorcery. The maidens on the Rock possessed the power of prophecy and correctly predicted the deaths of Arthur, Gawain, Morholt, and Gaheris.
Gawain and Morholt were trapped on the Rock after they decided to enjoy the maidens’ company. Yvain (Ywaine) tried to rescue them, but found that they had no memory of their former lives. They were eventually freed by Gaheris, who defeated the maidens’ brother in combat.
Sources
Post-Vulgate Suite du Merlin | 1230-1240
Post-Vulgate Queste del Saint Graal | 1230-1240