The story
Her one free night was with a stranger. By morning he was on the throne.
Isolde takes her sister's place as the Dragon Lord's bride, because it keeps her mother alive. He's a monster, and every bride before her has been torn to pieces. So before the wedding she gives herself one night of freedom, with a man she's never met. The next morning that man is sitting on the throne. It turns out her touch is the only thing that settles his curse, so she stays, planning to use his army for herself. Vael knows exactly what she's up to and lets her. Then she learns it was her own father who cursed him, and that Vael carries her poison. He hands her a blade, and she chooses the crown.