What descriptions about Zaroff’s physical features serve to warn Rainsford (and the reader) about the man’s brutal nature?

Zaroff isn't supposed to look like a standard villian. He actually looks quite refined and aristocratic. He does, however, seem to have a stern and aggressive undertone:

thick eyebrows and pointed military mustache were as black as the night from which Rainsford had come. His eyes, too, were black and very bright. He had high cheekbones, a sharpcut nose, a spare, dark face--the face of a man used to giving orders,