The monster resembles a human with dark-colored bandages wrapped around its head. The eyes are not visible through the wrappings but the creature's gaping mouth can be seen filled with long sharp teeth. Aside from the bandages, it only wears a tattered hospital robe. The monster also has skeletal hands with sharp claws and is barefoot.
It is encountered in the room where the player can find the key to the Isolation Zone. It is first seen hanging from a noose in a corner of the room, flickering in and out of visibility like an apparition. After the player takes the key, it disappears from the noose and the ambient music playing in the room suddenly stops. Leaving the room, it lets out a roar and the true chase begins.
This particular monster acts much like Specimen 6, only moving when the player is not making direct eye contact. Much like Specimen 6, it also randomly teleports away and continues its attack if the player stares directly at it for too long.
It always spawns from the door directly behind the player while entering a new room during its chase.
Monster 4 appears in the main game's Endless Mode, being one of many creatures who can randomly engage the player in a chase. It acts like it does in Karamari Hospital and has the same chase theme. It also has new hallucinations and a death screen.
Before chasing the player, the apparition of it hanging from the ceiling can be seen for a few seconds. When being chased, a foggy overlay clouds the player's vision.
When Monster 4 kills the player, a text shows up along with his death screen:
"Dark worms scream inside my brain.
Begging me to eat again.
Hearts, and blood, and bile, and soil.
I must consume to end turmoil."
"T-Rex Can't Wear Mittens", Monster 4's chase theme
Monster 4's death screen theme
- It functions almost identically to Specimen 6 from the main game.
- Monster 4 can move while being looked at, but only at a very minuscule speed.
- Notably, while it is chasing the player, Monster 6's hallway can still be accessed.
- While Monster 4 is chasing the player, Monster 3 will not appear in the hallways.
- The monster's death screen shows many screens, one of a human family, and another of a suicide note
- This gives evidence that the monster hanged itself.
- It is possible that Monster 4 represent Autophagia.