Unidentified ancilla (Installation 05)

The Cold Storage Monitor is a moving device that resembles a Forerunner Monitor. It is located on the ceiling of the Halo 3 multiplayer map Cold Storage, which is set in a small portion of a Flood Containment Facility on Installation 05. It is far larger than a normal Monitor, a comparison that can be easily made by entering Edit Mode in Forge.

Description
The Monitor, which is located in Cold Storage's main room, follows the movements of any players in the room, but stops paying attention to players when they leave the room. It is capable of seeing players using Active Camo, implying the usage of heat sensors or other optical technologies.

It has been speculated to be a "local caretaker," designated to watch over the facility like a prison guard, and similar in operation to a Human "dumb" AI. If that is the case, it can be viewed as having either failed or succeeded in its duties; the Flood Containment Facility has experienced an outbreak, but there are no Flood in the room that the Monitor resides in. The Monitor may possess offensive capabilities; while it has never been seen using an attack (and no attacks have been programmed for it in Halo 3), there is no other visible explanation for the lack of Flood in its chamber.

However, it is possible that this monitor has the same role with The Knowing, which is to gather and organize information about the course of history. This explains why these two monitors are similar as well as the reason that it failed to stop the flood outbreak.

The Monitor is apparently invulnerable to damage, and is attached to a pair of rails that run along the ceiling. It has not been seen using these rails, however, and in the game, it is programmed as an immobile piece of scenery.

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.
 * The Monitor will continue to watch the player after they have died, as long as no other player enters the room.