The Diamond Throne by David Eddings, 1989

Book One of The Elenium. Sparhawk, Pandion Knight and Queen's champion, returned to Elenia after ten years of exile, only to find his young Queen Ehlana trapped in a block of encelled crystal. Only the great sorcery of Sephrenia, ageless instructor of magic, kept her alive—but the spell would last only a year and its cost was tragically high. Now a Prince Regent ruled Elenia, the puppet of Annias, ambitious Primate of the Church who planned to seize power over all the land. As Sparhawk and Sephrenia set out to find a cure for Ehlana, Sephrenia revealed that there was only one person in the west who could defeat the evil plot against Ehlana. That person was Sparhawk. ISBN 0-345-36769-3.