Feast Of Souls: Magister: Book One by Celia Friedman
Against a backdrop of glittering kingdoms and dark prophecies, a rogue magister and a dying prince fight for their lives. Magisters from across the known world are gathering for an unusual meeting. King Aurelius has summoned them to heal his dying son, who has fallen victim to an incurable wasting disease. The King has demanded an explanation and a cure, yet appearances are deceptive. It's clear to the initiated that a magister is responsible - so the order remains quiet and organises a manhunt to silence the culprit. But while men are distracted, strangeness is stirring in the world. An ancient evil is rising in the north, but the old warnings are long forgotten. Only those carrying the Protector bloodline feel fear and their numbers are few. So the powerful will soon find themselves playing a new and more dangerous game.