Halo Alpha
Halo Alpha

Monitors are highly advanced Artificial intelligence constructs created by the Forerunners over one hundred thousand years ago to occupy special positions in Forerunner society. One of the main purposes of a Monitor was to be the caretakers of the Halo Array as well as other installations (such as the maintenance of Line Installations) and to ensure that the virulent Flood remain imprisoned. Monitors are extremely intelligent, yet completely devoted to their original function, and are zealous about containing Flood; Monitors have been known to violently turn on their allies if they should attempt to violate their containment protocols.

The Covenant refer to the Monitors as Oracles. Individual humans appear to use whatever names they deem appropriate; Sergeant Major Avery Johnson has referred to the Monitor 343 Guilty Spark as "light bulb," "tinker bell," and "robot," and both John-117 and Johnson simply shortened his name to "Spark."[1]


The body of a Monitor consists of a roughly spherical shape, concave on three sides, with an illuminated photoreceptor (an eye) located on the "front" of the orb. A Monitor's silvery metal covering is reminiscent of other Forerunner constructs, though their spherical shapes are a sharp contrast to the polygonal, angular shapes commonly seen in other Forerunner creations.  All of the Monitors seen so far speak in a male voice, not including 031 Exuberant Witness, that of whom speaks in a female voice.  Two have voices with a tinny but level quality while the other has a lower voice.

Monitors' eyes are branded with the Marathon symbol (except in Halo 2 and Halo: Combat Evolved Anniversary) and tend to have a variable hue. 343 Guilty Spark's eye color is blue (though it has changed to red during moments of what appear to be rampancy). 2401 Penitent Tangent's eye color is perpetually red despite no evidence of combat-related behavior other than his proximity to a Gravemind form. 049 Abject Testament has an orange eye. 031 Exuberant Witness, the monitor of the Genesis installation, has a purple eye color. Other colors observed include yellow, and green. During the SDCC 2011: Halo Universe Panel, a small video made by the "Sequence Group," shows Monitors that each have their own color.

Functioning and Behavior[]


2401 Penitent Tangent.

Each Halo Installation has at least one Monitor assigned to it, with Installation 05 having two: 2401 Penitent Tangent, and a large Monitor on a monorail, seen in Halo 3's Cold Storage.

Monitors have both numbers (presumably for identification) and names. The names appear to consist of an adjective describing a negative emotion followed by a technological term, though neither of the two names seen appear to have any specific meaning. In Forerunner communication logs, Monitors are identified by their Installation number (padded to two digits), a dash, and their own number; for example, 343 Guilty Spark, Monitor of Installation 04, is identified on such logs as "04-343."

Each Monitor commands the Constructors, Sentinels, Sentinel Majors, and Enforcers of the Installation they monitor.[2] The latter two are only activated if a catastrophic outbreak occurs, to hold back the Flood, while the Monitor locates a Reclaimer.

Monitors are extremely intelligent, but are also devoted to their original functions and to protocol, resulting in (among other things) a zealous attitude toward containment of the Flood and an overeagerness to activate the Halos. Monitors frequently cite protocols as explanations for their actions, no matter how impractical.This has been known to confuse or annoy modern-day humans who have interacted with them. It is possible that a Monitor sees their protocols as the only options in a situation; in Halo: Combat Evolved, 343 Guilty Spark could have taken numerous precautions to prevent the Flood from spreading across the Installation, but the only action he ever considered was the activation of the Halo.[note 1]

Nearly every action taken by a Monitor is based on some sort of protocol; even their greetings appear to be standardized. Of the two Monitors seen in the Halo series, both have introduced themselves as follows: "Greetings. I am [Number] [Name]. I am the Monitor of Installation [Number]."[3][4] The only variation seen is the occasional reversal of the latter two sentences.

Though a Monitor's knowledge of its own Installation is seemingly limitless, Monitors' knowledge is otherwise quite limited. In particular, 343 Guilty Spark does not appear to be able to distinguish between different Reclaimers until the events of Halo 2,[5][note 2] and the construct has admitted to lacking knowledge about other Installations, and it can be assumed that the Forerunners practiced this compartmentalization of information with the other Monitors as well.[1]

Monitors keep daily logs of all things that occur on their Installation. As with UNSC AI, the Monitors have been speculated to be in stages of Rampancy—a condition that affects human Smart AIs and is comparable to insanity—due to their isolation for literally a hundred thousand years.


According to Halo: Primordium, the Monitors were created using a device known as the Composer.

The process possibly resembles the way human artificial intelligence is made; scanning of neural network of a live human brain. 343 Guilty Spark was made using the mind of Chakas.

However, due to the advanced technology of the Forerunner, memory imprints known as Geas could possibly be extracted to become a Monitor without killing the human host. The process is still risky and could result in death.


Monitors seem to have a defensive resistance to small arms fire, though they will eventually succumb after taking extensive damage. In the novel, Halo: The Flood, John-117 fired half a magazine from an MA5B Assault Rifle at 343 Guilty Spark with no apparent effect; on Installation 08, John-117 was only able to destroy the Monitor with three blasts from a Spartan Laser, demonstrating that Monitors can sustain damage from high power weaponry. By comparison, a Spartan Laser can destroy virtually any other object in two shots or less. Should a Monitor be damaged, it is capable of self-repair.[6]

I am the m-monitor o-of installation z-zero f-four!

A damaged Monitor.

Though Monitors are assisted by other constructs in the event of a Flood outbreak, the Monitors also have their own offensive capabilities, including three types of beams. The first beam allows a Monitor to manipulate and levitate objects;[7] the second beam is a red-colored beam capable of depleting the shields of a Spartan-II in MJOLNIR Mark VI armor in a single blast and mortally wounding a less-armored human;[8] and the third is a blue beam that is primarily meant for unlocking doors on Forerunner structures, but that can also inflict minor damage upon targets.[1]

Monitors have the ability to teleport themselves and others around their Installations. It is unclear exactly how this teleportation works, but it seems that a Monitor on an Installation other than its own has no access to that Installation's transportation grid. It is possible that these limits are programmatic rather than physical; after hacking into The Core of a Halo, the human AI Cortana gained the ability to access the teleportation grids of all Installations, though her inability to access the power grids restricted her usage of the grid.[9] In Halo: Ghosts of Onyx, Dr. Halsey comments that Onyx's teleportation matrix is powered by a Slipspace generator of some sort; the Monitors may use similar technology when teleporting.

Known Monitors[]

Installation Monitor Name
00 (Ark) 000 000 Tragic Solitude
01 001 Unknown
02 007 Unknown
03 049 049 Abject Testament
04 343 343 Guilty Spark
05 2401 2401 Penitent Tangent
06 16807 Unknown

07 117649 117649 Despondent Pyre

If the Monitors in the Halo: Anniversary Terminal 2 were in numerical order, with 049, Abject Testament, as the reference point, the other Monitors' colors can be theorized.

  • Monitor/Clockwise/Counterclockwise
  • 001/Yellow/Green
  • 007/Blue-Teal/Pink
  • 049/Orange-Red
  • 343/White
  • 2401/Pink/Blue-Teal
  • 16807/Green/Yellow
  • 117649/Purple

The Monitor 117649 is purple in both orders, since it is opposite Abject Testament in the circle.


  • When the numbers of each Monitor are examined, a pattern emerges: each seems to be seven raised to the power of the Installation number minus one; therefore this grid can be founded. (7n-1=Monitor Number if n=The Installation's number.)
  • On the level The Ark, if you start at the second Rally Point and you betray all the Marines, Guilty Spark will fire his laser at you. Even on Easy difficulty, the laser is an instant kill. However, on the final level when you are supposed to kill him, his laser does not do significant, let alone immediately fatal, damage. This is likely for gameplay reasons and to discourage betrayal.
  • If you look closely in Halo: Reach, in Theater mode, you will see that the parts of a Monitor are not actually connected.
  • It is revealed in Halo 3 that the Monitors, or at least 343 Guilty Spark, have offensive capabilities very similar to that of a Sentinel, and can stun or immediately kill an opponent. 343 Guilty Spark primarily utilized this ability on two occasions in that game: once to destroy a Flood Combat Form that was about to attack Master Chief; and later to fight John and the Arbiter after mortally wounding Sergeant Johnson. 343 Guilty Spark may also use the effective beam on the level, The Covenant; when the player joins the Arbiter after defeating the two Scarabs, 343 Guilty Spark may fire at any enemy that gets too close to the bridge. He will also use it when the player kills too many Marines and causes all allies to shoot at the player.
  • The voice effect can be achieved by flanging, a technique often used for electric guitar.
  • In the multiplayer map Cold Storage, a large Monitor can be seen embedded in the ceiling which follows your movements, as long as you are in the same room as it. It appears to be attached to a monorail, though it never uses it.
  • In the Halo 2 Developer Commentary Playthrough, Martin O'Donnell, Jason Jones, and Joseph Staten jokingly referred to the monitors 049 and 007 as "49 Fucking Lightbulb" and "7 Broken iPod".[10]
  • A Monitor prop is unlockable for your Avatar on Xbox Live upon downloading Halo: Reach.
  • If the button for switching from Monitor to player is pressed repeatedly in Halo: Reach, the icon for the Focus Rifle will be seen in the Primary Weapon slot when in Monitor mode.
  • In Halo: Reach, if weapon and melee damage are set to 0%, the forge monitor will not explode if it leaves the battlefield. It will in fact fall and roll around if on a hard, sloped surface.
  • The monitors are very similar to the personality cores from the Portal series. Most notably, 343 Guilty Spark is similar to Wheatley in appearance and behavior.
  • It is revealed in one of the Terminals in Halo: Combat Evolved Anniversary that the 7 monitors of the Halo rings volunteered for their posting. They were originally monitors of other installations, with examples such as 686 Ebullient Prism of Line Installation 1-4.
  • On Halo: Reach Anniversary Firefight map Installation 04 a monitor can be seen if one heads to where in the campaign you head down stairs to find the hiding Marines but the door is closed but if you wait long enough the monitor is seen checking the area, it is speculated that he can be 343 Guilty Spark.
  • Halo 4 forge monitors are smoother, and appear more "low quality."
  • The Halo 4 Beam Turret fires a beam similar to that of a monitor.




  1. This behavior may also have been due to 343 Guilty Spark's possible rampancy. The Monitor may have literally been oblivious to all possible options that didn't follow protocol -- the Halo's activation may have been the only solution that ever even occurred to him -- and might not have been willfully ignoring other solutions.
  2. There have been multiple instances throughout the series in which 343 Guilty Spark has made various such mistakes; among other things, he once addressed John-117 as if he were Ur-Didact, and he was baffled when Reclaimers Avery Johnson and Miranda Keyes expressed no knowledge of protocol and The Ark. Whether this is a default behavior of Monitors or the result of Spark's apparent rampancy, however, is unknown.


  1. 1.0 1.1 1.2 Halo 3, The Ark (cutscene)
  2. Halo: Combat Evolved
  3. Halo: Combat Evolved: 343 Guilty Spark (cutscene). "Greetings. I am the Monitor of Installation 04. I am 343 Guilty Spark."
  4. Halo 2, Gravemind (cutscene). "Greetings. I am 2401 Penitent Tangent. I am the Monitor of Installation 05."
  5. "This Reclaimer is delicate." 343 Guilty Spark, emphasis added
  6. Halo: The Flood page 238
  7. Halo 3, Floodgate (cutscene)
  8. Halo 3, Halo (cutscene)
  9. Halo 2
  10. YouTube - VikingReact, Halo 2: Developer Commentary Playthrough (2007)