Creature — Rat
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Pack Rat's power and toughness are each equal to the number of Rats you control.
, Discard a card: Create a token that's a copy of Pack Rat.
The token will copy Pack Rat’s two abilities. Its power and toughness will be equal to the number of Rats you control (not the number of Rats you controlled when the token entered the battlefield). It will also be able to create copies of itself.