Noticed some strange behavior when using Mass Teleport on floor 4. Some moved monsters turned into white squares/tiles with their power listed on the white square. At least some hidden ("?") tiles stayed in place (such as the cyclops').
Unrelated, but something that would be nice to have is "endless" floors below the 4th. No achievements for them, just there to continue runs/for bragging rights. Probably easiest to generate them like a 4th floor but have the dragon increase in power each additional floor (possibly by more than 2) and/or apply a stacking sacrificial whip effect each additional floor.
It would be nice to be able to continue a good run to see how far you could take one.