Shadows of Fear (Combat)Source Ultimate Intrigue pg. 91
Your enemies’ fear causes them to jump at shadows, diverting their attention.
Prerequisites: Hidden strike +2d8 or sneak attack +2d6.
Benefit: The first time each round that you hit a creature suffering from a fear effect, you can deal hidden strike or sneak attack damage as if you were flanking that creature (improved uncanny dodge and other effects that prevent flanking also prevent a hidden strike or sneak attack from this feat).