Vallenna Rises: The Healer and the Warrior by Hayley Fulcher

She doesn’t expect Sebastian Thorne.

Heir to Vallenna’s most feared House, Sebastian is everything her father warned her against: ruthless, arrogant, and far too at ease with violence. But when he saves her life during the trials, Kara glimpses something beneath his mask. A man who would bleed for her.

Despite being promised to another, and a lifetime of never being allowed to choose, she falls for him.
Then Sebastian is accused of treason.
The sentence: Death.

Branded a traitor for stealing a Shard of the Arcanth, a sacred source of their world’s magic, he becomes the realm’s most wanted fugitive. And Kara is ordered to hunt him down.

But the deeper she follows his trail, the more she uncovers the terrifying truth: a new war is already on their shores, one that could shatter every House in the Vallenna.

Now Kara must make an impossible choice:
Turn him in and watch the man she loves die.
Or let him go, and burn with him.