Check the ice(?) slide between Icy Lake and Under the Ice. Since that's close to Under the Ice, might as well check there too.
You examine the Icy Lake and Under the Ice. Both reek of salted fish, and the slide is much less smooth. A colossal, gelatinous mass of once-living, flaming pickled fish-jelly now lays dead towards one side of the room, beneath the decorative wall mounted fish head that was already here.
The creature's been struck multiple times and frozen solid in chunks. The last few embers of its troubled existence are crackling. Mona quietly adds that Gadd should really remember not to store his experiments in the fridge ever again.
The crystals around the room have been somewhat shattered by the fight, scattering sparkling dust around the place. A large Treasure Chest sits opened. BELOWZERO is here, and it seems the final tape recorder was never played, because the host has a brain in the shape of the dead fish slime mass with the same current functionality. You press the button, and it seems its a bit of wait for the tape to crackle to life from paranormal static. This result will come shortly.
Finally, you note the RPG still remains hanging from the decorative fish head. Looking at it closer, it has one charge, labelled with a note in white marker that says "Point At Any Puzzle For Alternate Solution".