First Queen IV: Varcia Senki

Logris was once a land shared peacefully by elves, dwarves, and humans, the cultural differences between them never quite enough to spark a war. That equilibrium ends when the king of the northern nation of Barcia, Zenel—anxious about his nation's small population and precarious security—invites the dark magician Zon to strengthen his army. Zon's magic works, but the price is Zenel's sanity and the sanity of his forces. Barcia begins attacking its neighbors. A warrior named Ares attempts to assassinate the mad king and ends up imprisoned for the attempt, until a mysterious magic-wielding stranger frees him and reveals that the only path forward is to unite the races of Logris and march against the madness consuming Barcia.