Monster closet

A monster closet is a scare tactic used in Doom 3. They are very well hidden, the latter being visible only using noclip. When you near a monster closet, most likely a zombie or imp will jump out and attack you. It can catch players off guard, and they will become frightened. There are exceptions when Z-secs hide inside the monster closets, but it is rarely encountered.

Monster closets can sometimes be identified when walls or other areas fail to mesh with the surrounding architecture of what you've seen so far, and can activate upon entering the room, walking up to it, or passing right by and suddenly it pops open revealing your backside to the demon. Many of these closets often have powerups directly next to them, giving the player an incentive to move themselves towards the dangerous area unbeknownst to the unwary player. Upon grabbing the powerup, or just being near it, the closet will open.

This is not the same as a false set of security armor in one area of Doom 3 where upon going next to it, a demon resembling a Pinky Demon launches forward and bites the player before vanishing back through the same door. These are often actual powerups, ammunition, or armor lying around.