I'm going to be hosting an encounter where the PCs will enter a room. Behind the fully opened door in a hidden niche are three monsters that will attempt to close the door when the big bad gives the sign. My question is what is a simple way to handle the mechanics around the forcing of the door. The door itself is hinged on one side. By closing the door the three monsters are hoping to seal whoever is in the room in and whoever is out of the room out. The following things are what I am concerned with:
- What if one or more PCs is in the way of the door?
- If the PCs have not perceived the monster then there will be a surprise round where the door closing will occur. How does this affect the scenario?
- What's a fair way to include one of more PCs getting injured if the door closes on them (i.e. like getting an arm stuck in the door).