I believe that we can glean a hint of the answer in Mark Rosewater's latest State of Design article, from July this year
(It has "Tap any number of creatures you control with total power 3 or more: This token becomes an artifact creature until end of turn.") At the beginning of your end step, untap each other artifact creature you control
We like grouping these together so the page feels intentional instead of mixed in with regular full arts
from Warhammer 40,000 Commander to the deck with the idea that I can easily discount most if not all the generic mana part of the spells mana value by sacrificing creatures to Prossh
The eyes, its got great Sphinx cat similarities and its pose is akin to the Stadium boss tributing RubySapphire original ex
So, if you want to splash blue in your mono-red deck, Riverpyre Verge is perfect, since red is already your main color