The Belgariad 3, David Eddings

Many thousands of years ago, two prophecies came into being and a moment was fixed, when only one would determine the future. This moment, a clash between the maimed god Torak and the descendant of the Rivan king, is approaching . . . Garion, was brought up as a farm lad but is now beginning to understand the extent of his part in the prophecy, and working hard to control his sorcerous power.