Perfidy Feline

Devour 2 (As this enters the battlefield, you may sacrifice any number of creatures. This creature enters the battlefield with 2 +1/+1 counters on it for each creature sacrificed this way.)
Perfidy Feline may only sacrifice Rats.
"The cat warns her to say no more, but the mouse persists. The cat pounces on the mouse and eats her up. 'And such is the way of the world.' "