Rhodi's Rule. Crescent Empire: The Rhodi Saga, #5

Warriors will choose their path. The Cloaked Flame is gaining power, and a challenger has come to destroy the Rhodian throne. Dylan is the centerpiece of a new war, one where her enemies harness dark and cruel magic that's not only unpredictable, but relentless. To conquer her adversaries, Dylan must discover new aspects of her power, channeling a demigoddess who wants to use her magic more than help her cause.
Balancing the need to defend her people and the urge to understand herself, Dylan uncovers mysteries as her family crumbles around her and an unexpected revelation changes everything.  Devin is falling into shadow. As he investigates the Cloaked Flame's secrets, he finds himself sinking further into darkness. Fighting the Crimson warriors has caused Devin to relive the most devastating moments of his past, causing distance and strife between himself and the people he loves the most.
Reina may be the one who can heal his heart, but only if Devin allows her to bring him back into the light. Only one may claim the continent. The fate of the world will be determined by who wins the Crescentian Civil War, and the loser will be erased from the empire forever. If they're to survive the conflict, save their family and rise above the ashes, Rhodi must rule.