Kin & Kind - The Shard of Elan, #4

After generations of war, the fragile new peace hangs by a thread, as Ryuven attacks continue despite the treaty. Shianan leads an exhausted army facing a fresh and magically superior foe. Worried for Ariana, not yet returned from her own deployment, and as demoralized as his soldiers, Shianan is unprepared in every way when Flamen Ande, high priest of the Gehrn cult, reappears to demand Luca back. Luca was once enslaved to Ande, but that was a lifetime ago, before the fall of the shield, before the battle that nearly killed the prince-heir, before the desperate truce and the unexpected massacre by magics they could not resist.
But that was also only months ago, and thanks to Luca's devastating honesty, Ande is newly absolved by the court. Tamaryl has sacrificed too much for this peace, and he will do whatever it takes to preserve it-even bring more Ryuven to fight in Chrenada. When he is given a cruelly impossible choice, he must decide where his faith lies and who can be trusted with the salvation of his people. Ariana has irrevocably committed herself against the king's will, but that may be the least of her troubles as she is targeted by those who would use her for revenge.
Between human and Ryuven assailants, she must risk all on a defense no one else can use. Kin & Kind is the final novel in the action-packed Shard of Elan series!