Face-Stealer
Face-Stealers are creatures that can change their form to any other humanoid body. Unlike other shapeshifters, they can only change their shape after incorporating biological fragments of a person they wish to impersonate.
Face-stealers are sterile, as they are unable to reproduce sexually. They also physically do not have any sexual organs, and are unable replicate them when they transform into a new body. Organizations trying to root out face-stealer spies often resort to spot checks to ensure that their members have genitalia.
Their classification as a subspecies of shapeshifter is also debated, as they can be children of exclusively human parents. It’s theorized that the ability to shapeshift evolved independently from mutations from exposure to large amounts of magical energy, instead of being in the same lineage as Doppelgangers.