Monster 3 appears to be an abnormally large baby head with closed eyes, a wrinkled face, and an oval shaped mouth. The baby head is encapsulated in a rusted steel outline of a box. Its face glitches into a few different images.
Monster 3 is the first monster the player encounters while they are exploring the Secret Basement. It will appear in a select few rooms; spawning at different points within the rooms. When the creature appears, a contorted whine can be heard.
Monster 3 can float through walls; although it moves very slowly, making it easy to escape from if trapped.
It deals 16 damage to the player's health with a one second cooldown.
Monster 3 appears in the main game's Endless Mode, being one of the many creatures who can randomly engage the player in a chase. It appears in random places when player enters the room. Monster 3's chase is made significantly harder due to its fast attack speed, large hitbox, and the cramped environments of standard rooms.
"Old Experiments", Monster 3's chase theme
Noises heard from Monster 3 during a chase
- It is the only monster from the DLC that can reappear after being killed with the sword.
- It will not appear when the player encounters Monster 4.
- However, if the player kills Monster 4 with the sword, Monster 3 will start to appear in its rooms again.
- Monster 3 has the biggest hitbox out of all the enemies in the game.
- Monster 3's chase theme is the music from the hospital's basement.
The Monster has seemed to gain a new glitched head image. It no longer plays the ambient music of the Basement when chasing the player. Due to this, it is the only regular Specimen of the game to lack any kind of ambient track in Endless Mode (As Unknown Specimen 2 still overrides the music with its own "track", which is silent).
Monster 3 no longer reappears when killed with the sword. Whenever the player is not directly ahead of it, it stops moving and slowly turns towards them.
When attacking, it now makes a clanking sound instead of the regular damage sound, and deals 20 damage instead of 16.
Monster 3 seems to be faster than in the original. On the other hand, it can now be hit by the Axe or Sword, making it teleport away to a place in the room outside the player's field of view. Monster 3's new slow turning can be exploited to significantly slow down Monster 3 and potentially minimize the damage taken.
It now has its own starting room, which is a rusted metal catwalk that goes straight to the door, with an opening that has Monster 3 inside it.