The Tombs of Atuan (Earthsea #2)

When young Tenar is chosen as high priestess to the ancient and nameless Powers of the Earth, everything is taken away - home, family, possessions, even her name. For she is now Arha, the Eaten One, guardian of the ominous Tombs of Atuan.

While she is learning her way through the dark labyrinth, a young wizard, Ged, comes to steal the Tombs' greatest hidden treasure, the Ring of Erreth-Akbe. But Ged also brings with him the light of magic, and together, he and Tenar escape from the darkness that has become her domain.