Gabrielle Montaña only wanted to survive another night shift and pay off the crushing debts left behind after her father’s mysterious death But things don't always go as planned. One night inside a luxury nightclub in New Avalon, she witnesses something impossible, A man in a designer suit drinks from a woman’s throat like it is the most natural thing in the world, feeling frightened, she tries to run but Before she can escape, she is dragged into a hidden war between monsters who rule the city from the shadows. At the center of that world stands Núñez Francisco, a ruthless billionaire CEO feared in boardrooms and whispered about in the underworld But Nunez Francisco is more than a billionaire, He is the Alpha of the most powerful werewolf pack and the secret leader of the Syndicate that protects the supernatural world from human discovery. The moment Núñez scents Gabrielle, his wolf recognizes something impossible. She is his mate but the vampire court also wants her because Gabrielle’s blood is not ordinary. It is the Sanguine Key, a rare bloodline capable of sealing supernatural blood contracts that determine who rules the hidden world. So, To prevent a war that could destroy the Veil protecting humanity, Gabrielle is forced into a Blood-Oath marriage with the Wolf Billionaire. Yet the deeper she is pulled into Nunez’s world, the more she realizes she isn’t just a witness to the war, She is the weapon everyone has been waiting for And loving the wrong monster might ignite a war that could burn the entire supernatural world to the ground.