I had a good friend who was a Romulan. not literally, of course, but he could just be completely unnoticed in any room or group of people, to the point of startling them when he finally talked, even though he’d been standing there for minutes, born with a cloaking device. Exact opposite of charisma, two minutes later Sherlock Holmes would have a difficult time describing him; I played music with him for 17 years semi-professionally (he was a brilliant drummer) and it would still be hard to do a police sketch.
A stealther....