You put yourself in danger’s path to save your allies.
Benefit: While using the aid another action to improve an adjacent ally’s AC, you can intercept a successful attack against that ally as an immediate action, taking full damage from that attack and any associated effects (bleed, poison, etc.). A creature cannot benefit from this feat more than once per attack.
Advanced Player’s Guide. Copyright 2010, Paizo Publishing, LLC; Author: Jason Bulmahn.