[806mtson]

Wait, I think I know what the Power-Up Vistamps are based upon: Extinction Causers. Barid Rex is based upon the Ice Age, while the new Volcano Vistamp is based upon, well, Volcanoes. Volcanoes can cause Ice Ages, but also the Meteor which killed off the Dinosaurs also caused global temperature Drops, just like how the egg fell on Ikki during his first Transformation into Barid Rex.

So I think that Revice's Power Up Forms might be based upon Extinction Events just like how the Animals the Vistamps are based upon have extinct versions.

Entering "Speculation Zone". Between this and "Exiting 'Speculation Zone'" Line are all speculation

I think that the final Vistamp might be based upon Humans, because we are causing species to go extinct because of either the introduction of invasive species, purposeful hunting of them, climate change, destruction of their habitats for farming or for infrastructure, and/or even just by accident because of regular pollution. Humans really are an extinction event by ourselves. From driving Dodos to extinction because of Rats, to killing off Dire Wolves because they were killing our farm animals, to killing off the Tasmanian "Tiger", which wasn't even a tiger, more just a marsupial, to the Rhino Species which we drove to extinction because of poachers.

According to this article from nature.com on climate change, we are potentially driving up to a Million Species, maybe even more, to extinction because of just climate change.
https://www.nature.com/articles/d41586-019-01448-4

Humanity has a ton of skeletons in our collective closet.

Sorry for sounding like I am talking out of my rear end, but Humanity being the Final Form Vistamp would be kind of poetic. All from me realizing that Barid Rex was based upon the Ice Age and the Ice Age and Volcanoes both causing mass extinctions.
Exiting Speculation Zone.