The Tombs of Atuan

Ged is encountered years later in an dark, underground labyrinth by the young High Priestess Arha, also called Tenar. She was taken from her family as a girl to become a priestess to the Nameless Ones. Ged is a powerful wizard seeking the missing half of the Ring of Erreth-Akbe, on which is engraved the broken Rune of Peace. She makes him her prisoner, but sees that she is bound by meaningless ritual.