Corpsejack Menace is a uncommon Creature — Fungus card from Fallout (PIP), collector number 214. Current market price: $0.70 (foil $6.94), 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.