once both are on the field with a single Squirrel, you can sacrifice the Squirrel to Chatterfang, create a Treasure from the Plunderer, and Chatterfang will see that Treasure and create a new Squirrel
That flexibility alone makes it an auto-include in any blue deck
While I have obviously not played this strange un-format yet, I find the premise rather genius
Hector Javier Rosas Out of all of those abilities, I do really like how Sigarda, Herons Grace gives you hexproof and doesnt allow Emrakul, the Promised End to Mindslaver you, but overall I believe there are better options at the five-drop slot currently in Standard
A lot depends on how good both players are and how much of a read the players have on each other
Ruinous is not an understatement for the power of this iconic character, either