Heirs of the Enemy (Demonstone Chronicles #5‪)‬

The Alceans design devious traps that will help the odds facing them. They also set their sights on the heirs to the Federation thrones. A campaign of disinformation is also begun. But neither are Alutar's minions idle. The demons strike deep into the heart of Alcea, bringing death to Tagaret, and Alutar’s forces gain a decisive victory by finding something that was never supposed to be found.