The doors are always open after you clear a room unless I say it's a special locked room.
You pick it up, and notice that it was actually TWO keys, not just one.
You all proceed towards the next room.
After entering the rooms close on you again.
There are three, floating heads in here.
They screech as they see you, and start to spit balls of blood at you.
DC5 to kill them without getting hit.