The Night of the Swarm (Chathrand Voyage‪)‬

Robert V. S. Redick brings his acclaimed fantasy series Chathrand
Voyage to a triumphant close that merits comparison to the work of such
masters as George R. R. Martin, Philip Pullman, and J.R.R. Tolkien
himself. The evil sorcerer Arunis is dead, yet the danger has not ended.
For as he fell, beheaded by the young warrior-woman Thasha Isiq, Arunis
summoned the Swarm of Night, a demonic entity that feasts on death and
grows like a plague. If the Swarm is not destroyed, the world of Alifros
will become a vast graveyard. Now Thasha and her comrades—the tarboy
Pazel Pathkendle and the mysterious wizard Ramachni—begin a quest that
seems all but impossible. Yet there is hope: One person has the power to
stand against the Swarm: the great mage Erithusmé. Long thought dead,
Erithusmé lives, buried deep in Thasha's soul. But for the mage to live
again, Thasha Isiq may have to die.