Their debut in Rise of the Eldrazi needed to feel climactic and powerful, so they had to make a mechanic that felt appropriate for world-eating, unknowable, and unstoppable eldritch horrors
Target player draws X cards and loses X life, where X is the number of creatures they control of the chosen type
I think the Frenzy version is better overall Experimental Frenzy is incredible in the matchup, as it lets you just overwhelm the board with creatures and lets you dig deep into all your removal spells
Ogre Slumlord is here because they tend to group Squirrels with a few other creature types, including Rats
This collection has been making waves online, too
The American equivalent to this is usually 'Moderately Played' or 'Very Good'