Rise of a Hero — A.J. Cooper

The tenuous alliance between the cities of Eloesus evaporates. With the nation divided into the Thenoan and Kersican Leagues, war has become inevitable.
Out of the division, a new foe arises: the one called the Dark Captain. The Kersican League considers him the greatest of assets, but no one truly knows him or what lies beneath the surface.
The fourth book in the Wind of Destiny series.