After completing his Jedi training with Yoda, Luke was given a test: to enter a place filled with the dark side of the force. Entering into the place, Luke completes his assesment and destroys his adversary. After looking underneath the mask of his foe, Luke finds that the real enemy is actually himself. Tree climbing is no longer required at this cache.
"Fear is the path to the dark side. Fear leads to anger. Anger leads to hate. Hate leads to suffering."
-Yoda