You’ve become so adept at combating summoned creatures that you can interrupt the magical energies that summon them to your plane.
Benefit(s): When you use Dimensional Awareness to make an attack of opportunity against a creature being summoned or called into a square you threaten, you can additionally use an immediate action to attempt to send the creature back to its home plane. Attempt a Spellcraft check (DC = 15 + the creature’s CR [minimum 1] + the spell level of the spell that summoned the creature). If you succeed, the creature does not get to act and is immediately sent back to its home plane.
Pathfinder Player Companion: Monster Summoner’s Handbook © 2015, Paizo Inc.; Authors: Alexander Augunas, Tyler Beck, Anthony Li, Luis Loza, David N. Ross, Owen K.C. Stephens, and Linda Zayas-Palmer.