Magician's Gambit cover illustration by Geoff Taylor

Magician's Gambit by David Eddings
The third book in the Belgariad series 1981
Ce'Nedra, the Imperial Princess of Tolnedra, was confused. Everyone knew that the tales of the Orb that protected the West from the evil God Torak were just silly legends. But here she was forced to join a serious and dangerous quest to recover that stolen Orb.