The King’s Sword by Jennifer Anne Davis

From the moment Sabine set out for Lynk, her only thought was to find her sister’s killer. The answer comes with a terrifying discovery that puts her life on the line. Forced to trust her kidnapper in order to stay alive, Sabine embarks on a journey of harsh truths. Nothing is as it seems back in the palace among the clouds—especially the man she married.
On the run, Sabine and her unlikely ally seek refuge in Avoni—the kingdom known for its warring assassin guilds. The farther they go, the more hazardous their journey becomes as new enemies emerge. When unwanted feelings start to develop and secrets are uncovered, Sabine realizes there is no one she can trust but herself.
As Rainer’s wife, Sabine is nothing more than a pawn in a deadly political game that is decades in the making. When Rainer makes his next move, hinting at war, Sabine is ready with a countermove—and little does Rainer know, the pawn has become the queen, and she has no intention of losing with the stakes this high.