*spoilers for the ending*
Oh, and the ending! I meant to mention that. I admit that I was a bit disappointed at first: what happened, I wanted to know. How could you end there? But after thinking about it, it works really well for your dystopia. I expected, of course, that they would reverse the spell, land back in the common room, and wipe their brows in relief. But I actually love that you pulled that rug out from under me! It's so much creepier and dystopian that they can't escape! *shivers* REALLY nicely done. :)