Monitor

The Monitors were highly advanced Artificial Intelligence constructs created by the Forerunners 100,000 years ago to service and maintain the Halo installations and to ensure that the deadly Flood stayed imprisoned.

Monitors are extremely intelligent, yet completely devoted to their original function, and are zealous about containing Flood; Monitors have been known to turn violently on their allies if the latter 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 the Master Chief simply shortened his name to "Spark".

Appearance
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. The two Monitors seen so far speak in a tinny, but level, male voice.

Monitors' eyes are branded with the Marathon symbol 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 rampant or combat-related behavior, however. Whether eye colors vary between Monitors, between their action- or emotional states, or both, is unknown.

Functioning and Behavior
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. A Monitor's identification number appears to be 7 raised to the power of the Monitor's Installation number minus one. The names appear to consist of an adjective followed by a noun, 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. 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.

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]." 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, and the construct has admitted to a lack of knowledge about other Installations, and it can be assumed that the Forerunners practiced this compartmentalization of information with the other Monitors as well.

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.

Features
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, Master Chief fired half a magazine from an MA5B Assault Rifle at 343 Guilty Spark with no apparent effect; on Installation 04 (II), the Master Chief was only able to destroy the Monitor with four 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.

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 ; the second beam is a red-colored beam capable of depleting the shields of a Spartan-II in MJOLNIR Mark VI armor and mortally wounding a less-armored human ; 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.

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. 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

 * 343 Guilty Spark (Installation 04)
 * 2401 Penitent Tangent (Installation 05)
 * Cold Storage Monitor (Installation 05)

Trivia

 * 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.
 * 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 almost 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.
 * Monitors' eyes are branded with the Marathon symbol.
 * 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 the Chief 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.
 * It is possible that if a Monitor of an installation is destroyed, all Sentinels under its control will attack any beings on the ring. This theory is supported by the fact that after 343 Guilty Spark's destruction, all local Sentinels on Installation 04 (II) began to attack the Master Chief and the Arbiter. It is possible, however, that in his rampancy, the Monitor added the two to the Sentinels' targeting ledgers.
 * Guilty Spark's name is similar to Penitent Tangent; both Penitent and Guilty have very similar meanings:
 * Guilt (Guilty) - remorse or self-reproach caused by feeling that one has done something wrong.
 * Penitent - Feeling or expressing remorse for one's misdeeds or sins.
 * An alternative to the theory that the Spartan Laser simply deals so much damage that it can destroy a Monitor is that a Monitor's shields do not protect against light, which means that light-based weaponry, such as the Spartan Laser, could easily damage a Monitor. However, if the shields blocked light, Monitors would have no way of seeing; the theory is further contradicted by the ability of the Rocket Launcher and the Fuel Rod Gun to damage Spark's casing, albeit less efficiently. However, the Rocket Launcher and Fuel Rod Gun can only damage the Monitor after its casing and shielding has already been damaged by a Spartan Laser blast.
 * Another alternative to this theory is that Monitors can only be damaged by radiation; Laser stands for Light Amplification by Stimulated Emission of Radiation, and the Fuel Rod Gun uses radioactive Fuel Rods for ammo. If that was the case, however, the Rocket Launcher would be unable to damage 343 Guilty Spark.
 * 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.
 * On Halo 3 Legendary Edition, Martin O'Donnell, Jason Jones and Joseph Staten jokingly referred to Monitor 7 as "7 Broken iPod" and 49 as "49 Fucking Lightbulb".
 * All Monitors so far, with the exception of 2401 Penitent Tangent, have the same design as 343 Guilty Spark, examples including Forge Monitors and the Cold Storage Monitor.
 * For unknown reasons, Monitors (players in Edit Mode) in Halo 3 's Forge cannot be crushed between two objects, though they can take impact damage and can be injured by weapons fire.
 * It may be possible for the Flood to corrupt a Monitor, as in Halo 2, 2401 Penitent Tangent was relatively docile even under the Gravemind's control.
 * The Forge Monitors have lavender eyes, which would seem to imply that Monitors all have different colors.
 * On Co-Op, in the boss battle with 343 Guilty Spark on the Halo 3 level, Halo, if the player playing as Master Chief were to jump of the cliff and commit suicide, then Spark would watch the player fall, and keep watching the bottom, thus allowing the second player to easily kill him without a threat. This could be due to an AI flaw (in which the NPC only expects to fight a single opponent), though a canonical explanation could be insanity due to rampancy.