Between Fear and Favor by Jess Wisecup

The stakes are high, and the guilt runs deep. Haunted by their decisions, the King and Queen of Vesta must defend their kingdom and protect those they hold most dear—without losing themselves. With a city under siege, Emmeline and Rainier must do all they can to protect the ones they love; even if it means they might never see each other again.
With Cyran and Elora safely across the continent, wounds between mother and daughter will not be mended anytime soon. The princess must learn to master her newfound abilities while also mastering her grief—and her heart, thanks to the venomously handsome prince-turned-king.
Despite receiving no word from Lavenia and having knowledge of a dangerous turn of events with the dragon who accompanied her—Em and Rain hold out hope that not only is Lavenia alive, but has helped ally the seaborn to their cause. To do so would mean charming the tempestuous Sea Queen while navigating the hidden dangers beneath the waves. Lavenia has always been the foundation upon which her loved ones stand; will she crumble beneath the pressure?
And as trusted soldiers fall to the whims of the wicked, Nor’s safety becomes paramount. What would the Supreme do to get his hands on an heir to the Umbroth throne? Delivering her to a more secure hiding place becomes the responsibility of Dewalt, her most consistent adversary. With such proximity, will she tear down the walls he’s built around his heart? Or will he continue to be ruled by fear?
With the leader of the Myriad allied with the Nythyrian queen, desperate alliances must be forged, defenses must be fortified, and sacrifices must be made. Intent on delivering the Three Kingdoms from endless wars and violence, Em and Rain must petition a god for favor.
But will that be enough?