Relentless Rats is a uncommon Creature — Rat card from Magic 2011 (M11), collector number 113. Current market price: $5.07 (foil $5.92), TCGplayer market prices via Scryfall.
This creature gets +1/+1 for each other creature on the battlefield named Relentless Rats. A deck can have any number of cards named Relentless Rats.