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 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, which contains a single red eye and is filled with sharp teeth.
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, although it also occasionally teleport much farther distances. 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 the player has 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"
"100% Angus," Monster 5's Isolation Room chase theme.
"M7_AMB", 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".
- All the lines end in a period, with the exception of the last line. This may indicate that the last sentence is "Your tendencies have allowed me to make you forget."
- The monster might be the cause of the staff of Karamari Hospital (Nurse Tanaka, Dr. Tochigi and Dr. Hamada)doing actions that they don't remember,as it is indicated by its the death screen referring to the monster's ability to control the mind of the protagonist in order for him/her to "forget".
- The monster seems to be based off 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, a monster which resembles a bull.
- Monster 5 is referred to as "Ghost Cow" in the credits of Karamari Hospital.
- In both versions of its chase theme, a faint mooing sound can be heard.
- Monster 5 uses the same death screen noise as Monster 4.
- Walking into a dead end while the Monster is chasing the player will cause it to teleport inside them, ensuring a swift death if they are not near the exit to the maze.
Unlike in the base game, Monster 5 seems to have proper animations. The fog it creates is now much less rough looking, with black "smoke" covering the player's vision at times. The red ring surrounding the player's visions no longer flashes. Instead, a second ring closes in and out of the center of the screen.
Monster 5 is noticeably slower than it was in the original Karamari Hospital, likely to compensate for the player`s slower movement speed. It no longer teleports or passes through walls, instead just flying after the player (though it appears to "walk" with its horns). It does, however, phase through the door when it enters a room.
While the screen effect and music change happens in the first room of Monster 5's appearance, the rooms will only turn into iron bars from the second one onward.
In Endless Mode, hitting Monster 5 with the axe causes it to teleport to the beginning of the room, accompanied by the screen flashing blue. If the player hits it twelve times, it is defeated and the chase ends.