Gutter Grime is a rare Enchantment card from Innistrad (ISD), collector number 186. Current market price: $0.38 (foil $1.74), TCGplayer market prices via Scryfall.
Whenever a nontoken creature you control dies, put a slime counter on this enchantment, then create a green Ooze creature token with "This token's power and toughness are each equal to the number of slime counters on Gutter Grime."