The Last Sea King

This ninth novel of the Green Rider series follows the adventures of messenger, magic wielder, and knight Karigan G'ladheon This classic feminist fantasy series, beloved by decades of readers, is perfect for fans of Mercedes Lackey, Terry Brooks, and Anne McCaffreyGhosts are overrunning Sacor City's castle and streets. What begins as a nuisance soon turns serious when aggressive spirits overstep their bounds, harming the living.
As avatar of Westrion, the god of death, king's messenger Karigan G'ladheon should have been able to deliver the spirits to their afterlife destinations without any issue, despite the chaos. But Westrion's heart has gone missing, rendering her incapable of fulfilling her anointed role. Meanwhile, Akarion, the sea king of ancient days in possession of the body of the nobleman-thief, Lord Amberhill, leads nine fierce dragons and an army of his own people's dead-now more potent than ever due to Westrion's missing heart-to possess Sacoridia as his own.
And even as he rides, the dread master of Blackveil Forest, Mornhavon the Black, continues to build his own army to invade and conquer the lands of his enemies, intending to finish what he started a thousand years ago. Caught in the middle of these dangerous, converging forces, Karigan must find Westrion's heart quickly, lest malignant spirits and demons, freed from their prisons and under the control of those who covet godly powers, bring all the lands to ruin.