Re: Neil D/Louis D
The Phantom of the Opera himself. Also known as Erik, before Andrew Lloyd Webber decided to make him nameless. When he's angry, he unfortunately lashes out by killing people.
How much do you remember about what he does on this side? That might give you a clue as to what he wants, if you're not sure already. If he's the supervillain type then he probably won't be satisfied with causing trouble on just one side of the door.
[...] Research is our best bet. The more we know about them, the better we can control them. Weaknesses are a bonus. We have the advantage in that sense, and then we can start working on shutting them out and limiting their influence here.