Vacant

Vacants were a race of alien cuckoos that were dumped on planets. They started life as humanoid-shaped blobs, instinct drives them to take what they need from the dominant species on the planets. They begin with eyes and move on to shape their features before taking personalities to fill the vacant gaps by making eye contact and then putting their victims to sleep while they take what they need. Usually they blended in with the aspirations of an average person, although physically they were often quite striking as they were attracted to things of beauty. (TDL: The Pictures of Emptiness)