The Tombs of Atuan (Earthsea Cycle)

A wizard enters the underground domain of Ahra, high priestess of the Powers of the Earth, in an attempt to steal her palace's greatest treasure.

The second novel in the renowned Earthsea series from Ursula K. LeGuin

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.

With millions of copies sold, Ursula K. Le Guin's Earthsea Cycle has earned a treasured place on the shelves of fantasy lovers everywhere. Complex, innovative, and deeply moral, this quintessential fantasy sequence has been compared with the work of J.R.R. Tolkien and C.S. Lewis, and has helped make Le Guin one of the most distinguished fantasy and science fiction writers of all time.