Sylvar, General of Acorns

Other Squirrel creatures you control get +1/+1.
Whenever a Squirrel creature enters the
battlefield under your control, you may search
your library for a Squirrel card, reveal it, and put
it into your hand. Then shuffle your library.
"From the tiniest acorn, a mighty empire rises. Under
Sylvar's rule, the squirrels unite and flourish."