Whenever another Rat you control enters, exile up to one target card from an opponent's graveyard.
At the beginning of combat on your turn, create a 1/1 black Rat creature token with "This token can't block."
Flood the board with Rat tokens and aggressive Rat tribal beaters in mono-black, then close games with overwhelming swarm damage or a big payoff. Every combat you make a free Rat, and each Rat that enters chips away at opponents' graveyards to shut off recursion. You want to go wide fast and back it up with anthems, sacrifice value, or aristocrats payoffs.
Free token generation every combat builds a board with zero card investment
Graveyard exile disrupts reanimator, dredge, and recursion strategies incidentally
Cheap 3-mana commander gets going early and rebuilds quickly after wipes
Mono-black gives access to strong tutors, removal, and recursion
The Rat tokens can't block, leaving you vulnerable to opposing aggro and fliers
Go-wide strategy is extremely fragile to board wipes and sweepers
Color-locked into black means no access to protection, blue counters, or red burn
Without payoffs the tokens are small and easy to chump or trade away