Eternal Phoenyx by Stacy Reid — book slip

Princess Xian is caught in a web of political intrigue and forbidden desires. As the power of the Phoenyx awakens within her, she becomes a target for kingdoms eager to exploit her abilities.

With war looming, Xian must marry a man chosen by her king, but her heart yearns for Gavyn Westk'arr. A single night of passion with him unleashes a beast within Gavyn, igniting a love that defies duty and threatens to shatter their hearts.

Fourth in the Amagarians series.