Powerless by Lauren Roberts (Book 1: Powerless series)

Paedyn is a thief, a survivor, and above all—an imposter. After saving the life of Prince Kai, a ruthless heir to the throne, she becomes a competitor in the annual deadly Purging Trials, where the weak are eliminated for sport.

Thrown into the arena, she must survive without revealing her secrets, especially when feelings for the enemy prince begin to grow. But as betrayal, rebellion, and political tensions build, Paedyn must choose: protect herself or risk everything for those she loves.