Soulgazer by Maggie Rapier

Every legend has a beginning.

With their freedom on the line, a young woman and a rakish pirate take their fate into their own hands as they attempt to find a lost mythical isle with the power to save their entire world.

Saoirse yearns to be powerless. Cursed from childhood with a volatile magic, she's managed to imprison it within, living under constant terror that one day it will break free. And it does, changing everything.

Horrified at her loss of control, Saoirse’s parents offer her hand to the cold and ruthless Stone King. Knowing she'll never survive such a cruel man, Saoirse realizes there is only one path forward…she must break her curse. 

On the eve of her wedding, Saoirse seeks out the legendary Wolf of the Wild—Faolan, a feral, silver-tongued pirate. He swears to help rid her of the deadly magic, if she’ll use it to locate a lost mythical isle first. Crafted by the slaughtered gods, it’s the only land that could absorb her power.

But Saoirse knows better than to trust a pirate’s word. With the wrath of her disgraced father and scorned betrothed chasing them, Saoirse adds one last condition to protect herself: if Faolan wants her on his ship, he'll have to marry her first.