Tehanu: The Last Book of Earthsea

Evil thrives, and magic has been perverted. Everywhere there is fear and uncertainty; Wizards and kings want a woman from Gont to show them the way. Tenar, priestess of Atuan, cares for Therru, a girl who has known horror, and dedicates all her strength and wisdom to protecting her from her pursuers and coming to understand a world that is changing in a mysterious way.