They don't have a species name around here, because here there's only one species and they're pretty bad. Some worse than others, of course, because that's the way things tend to run.
Here, they're out of Hell. And I mean like... Christianity/Judaism's hell, I suppose. But if you're from a world with Olympus and all that, you might not know about that version.
They come out of there solely for being evil. They possess people, take them over completely, and go around being evil. They want the world to end by breaking seals that would bring up Lucifer, and he's pretty much this world's epitome of bad. Oh, and they seem to want us all dead.
But we have ways to stop them, it just isn't as simple as killing them. We'll teach it to everyone though.