Magician's Gambit (Book 3 of The Belgariad)

Garion, Belgarath, Polgara and their companions face new challenges as they continue their quest to retrieve the stolen Orb before it can be delivered to the evil god Torak.

When they reach the mile-high tower of Ctuchik, who has the Orb and whose followers practice Torak's cruel rites of human sacrifice, Belgarath must use all his strength, guile and sorcery as he faces his most fearsome enemy. Garion's strange powers continue to grow, as he plays an increasingly crucial role in this world'...