Marrow-Gnawer is a rare Legendary Creature — Rat Rogue card from Champions of Kamigawa (CHK), collector number 124. Current market price: $32.17 (foil $45.19), TCGplayer market prices via Scryfall.
All Rats have fear. {T}, Sacrifice a Rat: Create X 1/1 black Rat creature tokens, where X is the number of Rats you control.