The Sapphire Rose - The Elenium, Book Three
David Eddings

In returning to Elenia, Sparhawk risks delivering the power of the legendary jewel of life into the hands of an unholy triple alliance formed in the name of the evil god Azash. Sparhawk may have to unleash the full power of the jewel he calls the sapphire rose in order to defeat the degenerate sorcerer-king of the Zemochs, the renegade Pandion Knight Martel, and Annias, the traitorous church Primate who poisoned Queen Ehlana. But no one can predict whether the world itself will survive such an event.