Relentless Rats is a uncommon Creature — Rat card from Magic 2010 (M10), collector number 108. Current market price: $5.16 (foil $10.83), 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.