@SeraphimDawn
Or a brainwashy variety of cult, or some nosy reporter or researcher or investigator or what have you that has no regard for privacy and runs the risk of finding out things that maybe people shouldn’t know. I dunno, but let’s not limit ourselves.
And someone or something not fro Equestria or the human world could literally be anything. In a perfect world, Equestria Girls 3 would end with them killing Cthulhu with music. Don’t pretend you wouldn’t love that. You know you would.
I’d like for the next threat to come from somewhere other than Equestria. It can be native to the human world, or it can be from another world entirely, but there’s only so much that you have can send from Equestria to the human world without it starting to look like there’s nothing stopping you from just wandering from one into the other.