Monster 5 resembles a bull with wrinkled, hairless skin. The creature has a wide grinning mouth, crooked black horns, and small unblinking red eyes. The legs are bent downward at the knees as if they are broken and it has no visible tail. The monster's most prominent feature however, is that it is hanging upside-down by a long scrap of flesh connected to a levitating mouth filled with sharp teeth with a single red eye inside it.
Monster 5 is encountered while going through the maze to the Isolation Zone. It does not fluidly move, but instead, it constantly teleports very short distances ahead. It moves faster than the player can walk, so conserving stamina during its brief chase is strongly recommended when the player navigates the maze. This monster can not teleport through walls.
Monster 5 appears in the main game's Endless Mode, regardless of whether or not you have the Karamari Hospital DLC. During his chase the rooms begin to resemble the Isolation Zone maze from Karamari Hospital and a red, hazy effect overlays the player's vision. Unlike in the Karamari Hospital DLC, in Endless Mode this monster can teleport through walls. Every time the monster is in the player's vision, the screen flashes red. It has been given a new chase theme.
When player is killed by Monster 5, a text along with a death screen showing a brain will appear:
"Your fear allows me to enter your mind.
Your obligation allows me to control your hands.
Your reason allows me to break your eyes.
Your guilt allows me to loosen your neck.
Your expectation allows me to hide the truth.
Your tendencies have allowed me to make you"
Monster 5's Endless Mode chase theme
- The words fear, obligation, reason, guilt, expectation, and tendencies that appear in Monster 5's death screen form the acronym "forget".
- The monster seems to be based of Bovine spongiform encephalopathy (commonly known as mad cow disease), which is known to cause deterioration of the brain.
- The monster floating upside down with broken legs is also a direct reference to said disease (infected animals lose the ability to stand).
- Monster 5, along with the maze itself, may also be a nod to the story of Theseus and the Minotaur from Greek mythology. In the story, Theseus must escape from a maze that is inhabited by the Minotaur, which is a monster that resembles a bull.
- Monster 5 is referred to as "Ghost Cow" in the credits of Karamari Hospital.
Notably, walking into a dead end while the Monster is chasing the player will cause him to teleport inside the player, ensuring a swift death if the player is not near the exit to the maze.