Bound to the Guard by Sophie O’Dare

Kidnapped, stripped of his identity, and reduced to a number—now that Seven is free, he’ll make them pay.
His name is 07825, an unwanted Omega traded between ruthless men who despised his scent. Escape was never a dream, only a fleeting fantasy, until another captive offered him a way out. A map to freedom, but with only passage for one.
Alone, he follows the path and finds himself at Rockford Manor, home to the powerful Alphas who rule the city from the shadows. Seven owes his life to the man who helped free him, and he’s determined to deliver the message entrusted to him.
Standing by his side is Damien Rockford—older, commanding, and dangerously protective. Damien is everything Seven was taught to fear, yet the way he looks at him, as if he’s more than his scars, makes Seven feel safe for the first time in months.
Damien promises to destroy the men who hurt Seven, but first, they must return to the nightmare he escaped. As they grow closer, the pull between them becomes undeniable. But their searches tangle them in the experiments of Seven’s past. If they can’t uncover who’s funding it all, Damien might lose more than his heart—he might lose Seven forever.