Shifter's Eye

Your mastery of disguises has made you adept at spotting impostors.

Change form species trait or Disguise 5 ranks.

When you attempt a Perception check to pierce a creature’s disguise, you reduce any bonus it gains from any special ability it used to disguise itself (such as the +10 bonus to Disguise checks granted by disguise self or the change shape ability) by 5 or by an amount equal to your ranks in Disguise, whichever is greater. This can’t reduce the bonus granted by any of these abilities to less than 0.