From the Drowsy Mind of a Mouse

"Most glorious Prince of the Heavenly Armies,
Saint Michael the Archangel,
defend us in 'our battle against principalities and powers,
against the rulers of this world of darkness,
against the spirits of wickedness in the high places' [Ephesians 6:12]"
~ Catholic exorcism

I was in a dark, Hogwarts-like place. The surroundings were old and wooden, but sturdy-looking. There was a giant crowd of people around. I was on a second-floor platform, but you could look over the railing to see the first floor if you wanted. I looking for my friends, Caitlin (my pseudo-sister IRL) and Ken (a somewhat large lesbian, and one of my best friends IRL). I saw Caitlin and Ken run by me up the stairs, so I immediately turned around. I caught up to Ken, but Caitlin had gotten away. Ken informed me that Cait was possessed by The Demon.
In its natural form, The Demon looked like a small black cloud, but it could possess people and have them do its bidding. Ken and I had to get it out of Caitlin, so we were going to have to perform an exorcism.
I got Ken and we went to the dorm area of the hall. Some girl, with slight reluctance, let us set up a base in her room. It was a small, but cozy room with pale yellow walls. Once inside, we shut the door, lit a candle near the door and one near the bed, and I sprinkled a circle of Holy Water from the container that I had with me.

Layout of the room:
[].....~~...[.]
[]..~......~[.]
|......~~...[.]
|____'_'___|
The []'s make up a bed.
The ~ represent a circle of Holy Water.
The [.]'s are a desk with a TV on it and some papers that were on the ground.

There, we waited. I got prepared to say some exorcism. Suddenly, we heard a knock on the door. Ken went over to open it, but I stopped her.
"Who is it?" I asked.
No answer.
"Who are you?"
No answer.
"Should I turn out the lights?" Ken asked, about to suffocate the candles with her fingers. I nodded. The room got dark, and I kept the door locked. The Demon wouldn't be getting into this room.
I woke up.

This dream was quite frightening, but I don't know if it really was a nightmare. It had many nightmare qualities, like an unseen enemy, my friends are victims, and I'm not completely sure what to do, but during the dream, I was acting very calm, cool, and collected, although I really was quite nervous. I knew the precautions I had to take to stay safe. I'll just put it as a nightmare.
I should have noticed it was a dream because I don't believe in demons. I think crowds may be a growing dreamsign for me.