Erhnam Djinn

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.)

Mystery Booster 2

At the beginning of your upkeep, target non-Wall creature an opponent controls gains forestwalk until your next upkeep.

Vintage Masters

Judgment

Beatdown Box Set

At the beginning of your upkeep, target non—
Wall creature an opponent controls gains forestwalk until your next upkeep. (The creature is unblockable as long as defending player controls a forest.)

Anthologies

If you have more than one Djinn, you can have all of them target the same creature with their ability.

If there are no creatures your opponent controls to target at the beginning of your upkeep, ignore this ability.

In multiplayer games you can choose a different player's creature each upkeep. You are forced to pick a creature that some opponent controls if there is at least one creature on the battlefield that is a legal target.