Rock Tree Rage is a daily power available to the Barbarian class at level 19.[PrP:20]
Rock Tree Rage
Barbarian Attack 19
Your overwhelming strike calls the spirit of the great rock tree, rooting you and allowing you to lash out at approaching enemies.
Melee weapon
Trigger: An enemy enters a square adjacent to you
Target: the triggering enemy
Attack: Strength vs AC
Hit: 5[W] + Strength modifier damage.
Miss: half damage.
Effect: You enter the rage of the rock tree. Until the rage ends, whenever an enemy enters a square adjacent to you, you can make an opportunity attack against that enemy. In addition, if your are pull, pushed, or slide, you can reduce the distance of the forced movement by 2 squares.