From publisher blurb:
This particular installment of Exotic Encounters focuses on doppelgangers. While, in roleplaying games, they are typically depicted as shapeshifters, historically they were more akin to an “evil twin.” The first new type of doppelganger, the facestealer doppelganger (CR 1), cannot take any shape it desires, but rather must steal faces from its victims, leaving them as horrible faceless ones (CR 1/2). The cursed doppelganger (CR 5) is a more traditional take on doppelgangers, and cannot change shape, but rather appears as a single individual, whose life it attempts to destroy and then usurp. Finally, the mind drinker doppelganger (CR 8) is, in many ways, the ultimate doppelganger, able to copy not only appearances, but whole minds, using stolen memories to perfectly duplicate those it replaces.