Unidentified ancilla (Installation 05)

The Cold Storage Monitor is a moving device that resembles a monitor. It is located on the ceiling of the multiplayer map, Cold Storage in Halo 3. The "Monitor" follows your movements, but will stop once you leave the room. This Monitor is several times the size of an average Monitor, such as the player's model whilst in Forge. It has been speculated to be a "local caretaker," designated to watch over the facility like a prison guard, similar to a "dumb" UNSC AI. It seems to have failed as the Flood have mostly taken over the facility, although no Flood can be seen in the main room in which this Monitor resides, so perhaps, in a way, it has succeeded. This Monitor is also invincible, and cannot be harmed by grenades, human weapons, Sentinel Beams, or Plasma weapons. It appears that the "monitor" had the ability to move along a pair of rails that run along the ceiling, though, for whatever reason, it is now immobile.

Trivia

 * The Cold Storage Monitor will not follow a player in Monitor mode in Forge unless it sees the player before he/she becomes a Monitor. The Monitor will follow a new person that walks into the room, even if someone else is in there. This can be useful in Multiplayer battles like Oddball. An advantage, the Monitor can see everyone, even those wearing Active Camo. This indicates that it uses other sensors, such as heat sensors to detect objects that normally, cannot be seen.
 * In Red vs Blue: Reconstruction, the Cold Storage Monitor portrays a speaker system used by the Director and Councilor of Project: FREELANCER to communicate with Agent Washington in Chapter 19.