Where and when it shows up
Shift 2 and later. Appears on the ceilings of patient rooms and the front desk. Announced by a "Don't look up" on-screen message and a shift in the room's lighting.
This is the one monster where the "correct play" is literally just not engaging — the warning message tells you exactly what not to do, and following that instruction costs you nothing. The Eyedrops pacify option exists for situations where you need to work in that room and can't just avoid looking up indefinitely.