Oh, Sacred Dark by Marina Vivancos

Tyler’s first priority is to protect his coven. Not because he’s the High Witch’s right-hand-man. Not because he was born a Dom. But because this is his home, and a protector is who he is.
When a new person is fostered by the coven, Tyler is immediately suspicious. Roman is a sub, sure, but his old coven is bad news. They’re all convicted of practicing Chaos Magic, so…why isn’t Roman?
Tyler is sure that Roman is up to no good. The sub refuses to integrate with the coven. Will avoid meals, barely leaves his room, doesn’t talk to anybody. There’s something wrong there, and Tyler won’t stop until he finds out what.
Turns out, there’s a lot more to Roman than meets the eye—a dark past