The Heart of the Hill - Out of Avalon

The story "The Heart of the Hill" takes place after Arthur and Lancelot are gone and Morgaine is living on Avalon where only a few women are now sent to learn the old ways. One of those young women appears and reminds her of Gwenlian an old friend.
Most of the story is a flashback to the time when her friend was on Avalon. Gwenlian wanted to be more powerful and so she decided to seek out the Ompalos, a egg shaped stone said to give visions though it is against the rules for them to do so.
Conto de Marion Zimmer Bradley e Diana L. Paxson.