I find it weird, that you can collapse a bridge in Room 2, harming everyone in Room 11 which includes the Queen we are attempting to rescue. But she has no stat block so I don't know if she's dead or not. And if the flame monsters struggle to move when surrounded by ice and the entire keep is made of ice, how do they move? How do they retreat deeper into the place?
So many nifty ideas that the players don't really need to engage in, if they use some rope and go down.