Rodents of Unusual Size

Rodents of Unusual Size enters the battlefield
with a +1/+1 counters on it for each Rat you
control.
Escape—{b}{b}, Sacrifice 3 Rats or exile three
other Rats from your graveyard. (You can cast this
spell from your graveyard for its escape cost)
Buttercup: "Wait, what about the ROUS's?"
Wesley: "What, rodents of unusual size? I don't think
they exist."