This Realm could have falling trees, a maze, bears, forest fire, forest creature (like swamp realm) and the skill of this realm is to use short cuts and go off road.
Theory
There are 4 symbols on the wheel of power that are unidentified. This Realm might be one of them. Also for the realm helping cards there is a card called Forest Fire which saids to be use in Forest Realm.
So this is the most likely realm out of the 4 theory realm. also out of the 4 realms there is a leaf shaped symbol on one the wheel of power. It may be the forest realm.