Hypnotic voice. He can induce emotional effects in people by talking to them (making them feel calmer, happier, more fearful, more paranoid, more willing to do what he tells them to, etc. etc. etc.) Can be used subtly to influence interactions in his favor, or forcefully to drag someone into a particular emotional zone or push them to do something in the moment.

He can only induce one effect at a time, and targets can break loose from it with enough willpower, though it takes more effort to if he's using it forcefully.