Mr D is an alien, who runs the planetoid Eros like he owned it. He doesn’t really own the planetoid, of course. But he owns the air – or rather the life support facilities and pretty much everything – on the planetoid and uses mind control technology to control those working for him. He has turned the abandoned mines on the planet into an entertainment center for asteroid miners.
He is called mr D as his real name in somewhat unpronounceable for humans. Despite this he thinks he is passing for a human and likes loud clothes.