Erhnam Djinn is a rare Creature — Djinn card from Judgment (JUD), collector number 113. Current market price: $0.36 (foil $16.78), TCGplayer market prices via Scryfall.
At the beginning of your upkeep, target non-Wall creature an opponent controls gains forestwalk until your next upkeep. (It can't be blocked as long as defending player controls a Forest.)