Well, because the characters are all knew, I doubt anyone "knows why they are" yet. I think we'll see a new character for the main boss. With them will likely come a giant creature which does their bidding. They'll probably have a sorcerer or high priest who is secretly scheming to overthrow them. I'm thinking the new boss will have three or four soldiers who fight under them. They may be given terms like "assassin". Earthrealm will probably have a new hero, and there may be a character who watches, but you don't know what side he's on.
So that's nine or ten new characters right there. Of course, I may be way off, but that's what formula predicts.