Draco by Jayne Castel

The centurion with a heart of stone. The lady who scorns him. A marriage that will end the curse. Enemies to lovers in Medieval Scotland.
Draco Vulcan stopped caring about anything or anyone years ago. Cursed to live forever, he only finds joy on the battlefield. But in order to break the curse upon him and his friends, he must wed a woman he can’t stand.
The lady in question has just escaped a loveless marriage. The last thing she wants is to enter another one—especially to the cold, brutal warrior who fights at William Wallace’s side.
When the English king hears that Wallace is hiding at Dunnottar Castle, and lays siege to the fortress—Draco and the widow must band together against this common foe. But are they prepared to take things a step further and sacrifice their own happiness to break an ancient curse?