"Scourge of the Overlord" by Rick Skowronski and E. C. Skowronski (Book 3)

Assaulted by monstrous and terrifying foes from without, and betrayed by treachery from within, Syren and her friends are forced to abandon the tenuous security of hearth and home. In her absence, the malevolent forces of Stormwood tighten their stranglehold around the frontier village of Westpost. Estranged from the town and people she loves, Syren and her friends delve the depths of the forest and beyond. There, they discover a new ally, and even more powerful and disturbing sources of evil.
Can Syren live without her beloved Westpost? Can Westpost survive without Syren? Punishment and peril reach a climactic peak as the heroes race to rescue town and townsfolk from a coalescing and relentless evil.
Don't miss this epic conclusion to the Westpost Trilogy!