Druuth Slayer( Champions of Valor, p. 29)
You have studied the lore of the druuth (a cabal of doppelgangers led by a mind fl ayer) and know how to recognize and resist their powers.
Knowledge (dungeoneering) 2 ranks, Knowledge (nature) 2 ranks,
This feat grants three benefi ts. First, you get a +1 bonus on Will saving throws. Second, you gain a +10 insight bonus on Spot checks made to recognize a doppelganger using its change shape ability. Third, if affected by a mind fl ayer's mind blast, you get a new saving throw every round at the end of your turn to end the stun effect.