The Sworn - The Fallen Kings Cycle: Book One

As plague and famine scourge the Winter Kingdoms, a vast invasion force is mustering from beyond the Northern Sea. And at its heart, a dark spirit mage wields the blood magic of ancient, vanquished gods. Summoner-King Martris Drayke must attempt to meet this great threat, gathering an army from a country ravaged by civil war. And neighbouring lands reel toward anarchy while plague decimates their leaders.
Drayke must seek new allies from among the living - and the dead - as an untested generation of rulers face their first battle. Then someone disturbs the legendary Dread as they rest in a millennia-long slumber beneath sacred barrows. Their warrior guardians, the Sworn, know the Dread could be pivotal as a force for great good or evil. But if it's the latter, could even the Summoner-King's sorcery prevail?