1. At least one of them will die from a lack of proper air to breathe.

2. The human will likely brand the surviving demon as unholy and attempt to kill it. The fight's result will depend on what weapons were carried into the room.

I think that will likely happen. Unless of course that human is pretty freakin' open-minded.

Oh, and Shim, you forgot that tribal pact in the mountains east of the Dominion. It barely surrounds the mountains and is land-locked.