"For all I know, perhaps they do." Degas shakes his head. "Notably, tieflings--descendants of demons with human blood--aren't purely evil, and many exist who defy their demonic blood. Not all do, though. They have choice, like humans do. And that's before we get into the complicated natures of extraplanar entities like the Fae, who also have a clear division into the Seelie and Unseelie courts."