Giant Slug is a common Creature — Slug card from Chronicles (CHR), collector number 33. Current market price: $0.11, TCGplayer market prices via Scryfall.
{5}: At the beginning of your next upkeep, choose a basic land type. This creature gains landwalk of the chosen type until the end of that turn. (It can't be blocked as long as defending player controls a land of that type.)