The short version
The entity players call the Skinwalker is officially the Mimic: the fan wiki records the rename and a crawl-on-all-fours animation added in the July 10, 2026 update. Its identity is the layer trick — a patient that passes the live window and the photo, then reveals a wide, sharp-toothed form or a void-black body on the CCTV feed. The camera mismatch is the decision clue, and the response is the shutter reject at reception; rejected patients are even reported to come back later as Mimics that bang on the window.