Ok, time to tear.
I too felt like I was reading about a new recruit to X-Men. If this is your source, I would seriously consider changing the plot, cause it's been done.
Ok, I like to start off with the 'nit-picky' stuff first, grammar, spelling, structure....
Your internal dialog of the character needs to be more obvious, here are a few times when you could maybe put his thoughts in italics to help the flow:
Oh right, everything was at the dorm
Why had they picked him, of all people?
Ok, I had several problems with the story. I know that I usually tell people to get to the conflict quick so you can hook the reader, but in your case I would SLOW DOWN. (just me, others might disagree). I really like how it started, the MC is great, I like him. I like how he comes in and waits at the airport...but the whole monster/shadow thing happened so fast that I was left feeling...well...I didn't like it.
Here are some things that bothered me.
Amazingly, the monster backed away a little bit. They could be hurt!
I never assumed they couldn't? Are we supposed to assume that they are invisible?
It screeched, almost sending Thomas to his knees. Almost, but not quite.
- Almost but not quite? You just said before that it "almost" sent him to his knees? It is redundant to put that last part in.
It seemed that the smaller shadows at least couldn’t go through doors.
Once we are left to assume that the shadows can penetrate things? I must have missed something.
Anise turned and smiled at him for an instant before going back to swinging with the extinguisher. Thomas could feel himself blush again.
This part and the end when he gets her number was wayyyy to rushed. They are flirting in the midst of a monster chasing them? The last thing they would be thinking about would be flirting and getting someones number. Make this a traumatic event, not an everyday occurrence. This girl seems like she is only part of the story because you want a romantic interest for your MC. Remember in Writing Excuses they talked about this pitfall. Give the girl more depth and THEN make your main character fall for her.
Thomas’ mind gibbered
Gibbered? New word for me...but...I liked it...if it is a word.
The creature tried to spew those black bullets of shadow stuff
I agree with wcarter4, this description needs serious work.
With no more apparent effort than picking a grape, it pulled.
Didn't care for this personally.
“Come on, we should get out of here before people come to look at the destroyed door.” Anise said.
Why is she worried about that? They just got attacked by a monster...seems trivial to be worried about that.
Ok, this really bothered me:
Well, there was that mass hallucination, but that wasn’t real, and he got a girl’s number out of it. He wondered what chemical they put in the ventilation system to do all that.
Your MC writes off the whole thing WAY to quickly. I was really bugged by that.
Ok, this was probably the hardest critique I have given, and I apologize if I came off negative. I like the story, don't get me wrong, but it was just too rushed. I liked the idea of this kid who is supposed to be smart, but he doesn't see it. Maybe work bringing in the whole mask thing later in the story. Just have a monster attack them in the beginning, but make it vague. Leave your readers wondering, "what the heck was that?". Don't over describe the monster, you leave us to no imagination.