The Hospital Creature is a minor antagonist in the third season of Stranger Things. It is a monstrous fragment controlled by the Mind Flayer composed from the flesh of Tom Holloway and Bruce Lowe, two infected humans.
The Hospital Creature first appeared after Nancy and Jonathan fought and killed Tom Holloway and Bruce Lowe separately. The two infected humans' bodies dissolved into flesh and then merged into the creature in a hallway.
As soon as it is complete, the creature soon saw the pair and started to chase after them, throughout the upper part of the hospital. While Jonathan managing to evade the creature, it continued on pursuing Nancy to a room in the building, where the latter closed the door on it; however, the creature simply melted and crept underneath the door, re-solidifying on the other side. It then moved to attack Nancy while Jonathan, noticing the bits of the creature sliding in the door prior, tried to break into the room.
At the last second before the creature would kill Nancy, Eleven arrived with the kids, breaking down the door with her powers before beating the beast by slamming it to the walls and brutally throw it out of the hospital. The creature, though weakened, slithers into the sewers.
It will then later be integrated, and by extent Tom and Bruce, into the Mind Flayer's physical "proxy" form.