The Stone of Tears by Terry Goodkind

In denying his heritage, Richard Cypher, grandson of the last true Wizard, ignores the Wizard's Second Rule. It may be his undoing and the Lands'. One person holds the power to make Richard accept what he hates-Kahlan Amnell, Mother Confessor. To save her people, her world, and Richard, from the Keeper of the Underworld she must sacrifice everything she holds dear and begin a war she knows can only end in death. 

Darken Rahl, from beyond the veil, has begun to summon a sinister power worse than any he has wielded before. Armed with the Sword of Truth, Richard Cypher, now become Richard Rahl, must learn to control his own new-found power; or the world will spin into darkness unending. The Sisters of Light promise help. While Richard journeys to their forbidden city, his beloved Kahlan sets out for Ayindril, citadel of the old wizards, in search of Zedd and the help only he can lend. 

War, suffering, torture, and deceit lie on their paths. So, also, does their destiny... This is a world where the creatures of nightmare will find you by the movement of a shallow breath and waking dreams will decide your soul's fate... Where magic is both a boon and a bane to those who use it and those who merely feel its touch.