You shove your opponents into each other or into a wall, causing painful and damaging collisions.
Prerequisites
Strength 13, Power Attack, Improved Bull Rush.
Benefit
When you bull rush an enemy and its movement is stopped by a solid wall or barrier, it takes 1d6 points of bludgeoning damage, plus an additional 1d6 points of bludgeoning damage for every 5 feet your target has moved as a result of your bull rush.
When you bull rush an enemy into another creature, both creatures take this damage, and the bull rush movement ends. If you choose to continue pushing both targets, this impact deals no damage. If a second impact occurs, each creature takes damage based only on how far it was moved after the first impact.
For instance, if you successfully bull rush a goblin 10 feet and it then collides with another goblin, both creatures would take 3d6 points of bludgeoning damage.