The Hope of Vitality by Allan N Packer

Desperate to free the royal hostages, Will Prentis and King Krasmir of Rogand face off against the scheming Grand Vizier of Ahr. As the specter of war looms ever larger, only the emperor of Ahr has the power to avert catastrophe.

With the Grand Vizier remaining a step ahead of his enemies, a mysterious captive might hold the key to exposing his objectives.

Everything will depend on three remarkable talismans and the courage of those bearing them into deadly peril.

Note: The Hope of Vitality is book six of the Stone Cycle, a multi-part saga that ends with this final installment.