Corpsejack Menace is a rare Creature — Fungus card from Return to Ravnica (RTR), collector number 152. Current market price: $0.57 (foil $0.94), TCGplayer market prices via Scryfall.
If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on it instead.