Changelings and Dopplegängers

 I took this picture from Where the Shadows Stalk of the sadly short lived Forbidden Gateway  gamebook series. This is a monstrous humanoid made of vegetals that is turning into a copy of your character. A sort of dopplegänger, although they call him a Changeling. It is the first adversary you fight in the book and it truly sets the tone for the kind of horrors you will face during the rest of the adventure. I find dopplegängers and changelings scary and unsettling (you can be replaced by an usurper, someone you love and trust may not be who they are, etc.), but is it me or are they seldom used nowadays in horror? They deserve a comeback. Anyway, if you know of any stories involving them, let me know in the comments section.