You deflect attacks that could mean your ally’s death.
Prerequisite: Shield Proficiency.
Benefits: Whenever an adjacent ally is the target of an attack, you can, as an immediate action, grant that adjacent ally a +2 shield bonus to AC. You must be wielding a light shield, heavy shield, or tower shield to use this feat.
Advanced Player’s Guide. Copyright 2010, Paizo Publishing, LLC; Author: Jason Bulmahn.