Spitting Slug is a uncommon Creature — Slug card from The Dark (DRK), collector number 88. Current market price: $1.83, TCGplayer market prices via Scryfall.
Whenever this creature blocks or becomes blocked, you may pay {1}{G}. If you do, this creature gains first strike until end of turn. Otherwise, each creature blocking or blocked by this creature gains first strike until end of turn.