Prince of Agony by Tavia Lark

The price of Kazia’s power is pain.
Prince Kazia Dire isn’t nice. Being nice lets people close. Letting people close risks revealing Kazia’s greatest secret—the power that condemns him to a lifetime of abuse.
Until opportunity appears in the form of a captive enemy mage.
Following a dragon across the border lands Lucien Vaire in chains, and matters only get worse from there. Lucien has hated House Dire since the last war. Now, he’s under the notorious brat prince’s direct control.
Yet beneath Kazia’s vicious mask, Lucien senses desperate vulnerability.
Painful experience has taught Kazia to fear mages. He needs to keep Lucien at a distance even as he uses Lucien’s talents. But that distance narrows with each careful kindness. Each accidental touch. Lucien acts more like a protector than a prisoner, and Kazia is tempted by the dangerous sweetness of trust.
But Lucien is still a mage, and Kazia is still broken. And Kazia’s cruel parents may still destroy them both.