Halo Array: Difference between revisions

{{Era|Forerunner|Covenant|HCW|Post|FA}}

[[File:TerminalArkArray.jpg|thumb|right|300px|The Array at [[Installation 00]], just before their departure to firing sites across the galaxy.]]

{{Quote|Halo doesn't kill Flood, it kills their ''food!'' Humans, Covenant, whatever—we're all equally edible! The only way to stop the Flood is to starve them to death. And that's exactly what Halo is designed to do: wipe the galaxy clean of all sentient life!|[[Cortana]] during the [[Battle of Installation 04]].<ref name="TB">'''[[Halo: Combat Evolved]]''', campaign level ''[[Two Betrayals]]''</ref>}}

The '''Halo Array''', sometimes known simply as '''Halo'''<ref>''[[Halo: Warfleet]]'', p. 92</ref> or '''the Array''',<ref>'''[[Halo 3]]''', ''[[Terminal (Halo 3)|Terminal Four]]''</ref><ref>'''[[Halo: Combat Evolved Anniversary]]''', ''[[Terminal (Halo: Combat Evolved Anniversary)|Terminal Two]]''</ref> is a network of colossal ring-shaped superweapons individually known as '''Halos''' or '''Halo rings''', constructed by the [[Forerunner]]s.<ref>'''Halo: Combat Evolved''', campaign level ''[[The Truth and Reconciliation]]''</ref> The Halos were also referred to by the [[Covenant]] as the '''Sacred Rings''',<ref>'''Halo: The Flood''', page 38</ref><ref name="gravemind">'''Halo 2''', campaign level ''[[Gravemind (level)|Gravemind]]''</ref> and labeled as '''Installations''' or infrequently referred to as Fortress Worlds<ref>'''Halo: The Flood''', ''page 193''</ref> by the Forerunners and their [[monitor]]s.

The first array of twelve Halos was constructed by order of [[Master Builder]] [[Faber]] circa [[98,445 BCE]] with the intent of being an ultimate weapon, one that would secure the preeminence of the [[Builder]] [[rate]] in Forerunner society.<ref name="c274">'''Halo: Cryptum''', ''page 274''</ref> Later, the weapons would be refined further and a new array of six smaller and significantly more lethal installations was constructed; the newer Halos are known as the "neoteric" rings.<ref name="neoteric">[https://www.reddit.com/r/halo/comments/70wbxc/return_to_the_denomination_installation_04_b_c/dn76nzc/ ''Reddit: Return to the denomination. Installation 04 (B), (C). Canonically. 343 PLS (comment by GrimBrotherOne)]</ref> Eventually, eleven were destroyed and/or lost while the remaining [[seven]] were used by the Forerunners as a last resort when combating the parasitic [[Flood]]. All [[sentience|sentient]] beings in the galaxy were killed, robbing the Flood of hosts and starving it to death.

In addition to serving as weapons of last resort, Halo installations are also research facilities dedicated to containing and studying many different kinds of life forms. The life forms that were hand-selected by the [[Librarian]] included marine life, fauna, and land vertebrates. With the Master Builder's permission, the Librarian would research each animal to detect if their bodies reacted to Flood infection. The research on the animals would be more deeply analyzed if they did become infected. The Librarian's studies also helped determine if the rings could be used to repopulate the galaxy as part of the [[Conservation Measure]].<ref name="c313">'''Halo: Cryptum''', ''pages 313, 334''</ref>

As it is known in modern times, the Halo Array is a network of seven ring-shaped megastructures created by the Forerunners, designed to exterminate all sentient life within the Milky Way galaxy.<ref name="great journey">'''[[Halo 2]]''', campaign level ''[[The Great Journey]]'', ('''343 Guilty Spark:''' ''"After exhausting every other strategic option, my creators activated the rings. They, and all additional sentient life in three radii of the galactic center, died, as planned."'')</ref> Built following the [[Human-Forerunner War]], these ringworlds were later used as a last resort against the Flood, a parasitic extra-galactic species that threatened to consume every sentient life-form in the galaxy. By activating the rings, the Forerunners wiped out every sentient being in the galaxy, effectively starving the Flood to virtual extinction, though specimens were kept in a number of Forerunner [[Flood containment facility|containment facilities]], including the Halo installations themselves.<ref name="library">'''[[Halo: Combat Evolved]]''', level ''[[The Library]]''</ref>

A total of eighteen Halo rings existed during the reign of the Forerunners; an older array of twelve 30,000-kilometer-wide rings produced by the [[greater Ark]] and six 10,000-kilometer rings, constructed at the newer [[Installation 00|lesser Ark]]. Of these, only seven survived to be included in the final Array. The Halos were originally deployed in orbit over large gas giants.<ref name="gas giants">'''Halo: Silentium''', ''page 237''</ref> However, as of [[2557]], [[Installation 03]] orbited a rocky planet.<ref name="h4composer">'''Halo 4''', campaign level ''[[Composer (level)|Composer]]''</ref> Installation 04 maintained an atmospheric [[Threshold gas mine|mining facility]] in its anchor planet [[Threshold]]'s atmosphere until [[Battle of the Threshold gas mine|it was destroyed]] by the [[Covenant]].<ref>'''[[Halo 2]]''', level ''[[The Oracle]]''</ref>

Though separated by thousands of light-years, the installations are networked together and capable of remote activation at [[Installation 00|the Ark]], their [[intergalactic space|extragalactic]] construction foundry. Each Halo installation has a maximum effective range of 25,000 light-years in every direction.<ref>'''Halo: Combat Evolved Anniversary''', ''[[Terminal (Halo: Combat Evolved Anniversary)#Terminal 8|Terminal 8]]'' (''"25,000 light years. That is the effective range of this installation."'')</ref><ref name="radius">'''[[Halo: Combat Evolved]]''', level ''[[Two Betrayals]]'', 343 Guilty Spark: ''"Technically, this installation's pulse has a maximum effective radius of twenty-five thousand light years."''</ref> The method utilized by the array to conduct this "mass sterilization protocol"<ref>'''[[Halo: Combat Evolved]]''', level ''[[The Library]]'', 343 Guilty Spark: ''"Why the Flood is, naturally, simply too dangerous to release, and mass sterilization protocols may again need to be enacted."''</ref> involves the superluminal conveyance of a burst of cross-phased super-massive neutrinos, tuned to emit a harmonic frequency that destroys the nervous system of any life form within range. Simpler organisms lacking a neural system are unaffected, along with inanimate structures. [[Precursor]] technology, however, is extremely susceptible to damage from the Halo effect due to its quasi-living [[neural physics]] composition.{{Ref/Reuse|c274}}<ref>'''Halo: Cryptum''', ''page 132''</ref>

The Halo Array in its entirety has been fired only once in known history, approximately 100,000 years ago, by the [[IsoDidact]] in order to stop the Flood from overwhelming the galaxy. All beings in the Array's effective range, including Forerunners themselves, were wiped out by the Array's pulse,{{Ref/Reuse|great journey}} with the exception of those who took refuge on the [[shield world]]s. A number of Forerunners survived at the lesser Ark but chose to exile themselves from the galaxy.<ref name="rebirth">'''Halo: Rebirth'''</ref> The array has come close to activation four times since; Installation 04 was almost activated by the [[John-117|Master Chief]], Installation 05 was activated by Commander [[Miranda Keyes]] at the behest of the [[Jiralhanae]] [[Chieftain of the Jiralhanae|Chieftain]] [[Tartarus]], [[Avery Junior Johnson|Sergeant Johnson]] was forced by the [[Prophet of Truth]] to activate the Array from the Ark, and [[Bobby Kodiak]] was forced by [[000 Tragic Solitude]], the Monitor of the Ark, to activate the Halo Array from the Ark as a revenge. None of these attempts were successful; the first was stopped by Cortana, while the other three attempts were halted by UNSC and [[Swords of Sanghelios|Sangheili]] intervention. A [[Installation 08|replacement]] Halo for the destroyed Installation 04 was successfully activated outside of the galaxy, eliminating the Flood massed at [[Installation 00]], but it was incomplete and thus not networked to the rest of the Array.<ref name="halo3halo">'''[[Halo 3]]''', campaign level ''[[Halo (Halo 3 level)|Halo]]''</ref>

Each of the Halo installations manufactured at Installation 00 is given a sequential designation number based on their order of construction, beginning from 01,<ref name="construction order">[https://www.reddit.com/r/halo/comments/70wbxc/return_to_the_denomination_installation_04_b_c/dn6zt7s/ ''Reddit: Return to the denomination. Installation 04 (B), (C). Canonically. 343 PLS'' (comment by GrimBrotherOne)]</ref> and is overseen by a single [[monitor]]. The monitors are given control of the Installations' [[Sentinel]] automatons, from [[Sentinel Aggressor|Aggressors]] to [[Constructor]]s and [[Enforcer]]s, and are responsible for containing the Flood test subjects in their [[Flood research facility|research facilities]] and protecting the Halo from intruders.

The Array also encompasses [[Installation 00]], an extragalactic construction facility that can create replacement installations in the event that one is destroyed. All Halos can also be remotely activated from the Ark without being subjected to their effects, as the megastructure is out of the Array's range.<ref name="thecovenant">'''Halo 3''', level ''[[The Covenant (level)|The Covenant]]'', '''343 Guilty Spark''': ''"The Ark is out of range of all the active installations!"''</ref> The Forerunners also built [[shield world]]s as a means to escape the effect without having to leave the galaxy.<ref>'''Halo: Ghosts of Onyx''', ''page ??''</ref>

Twelve Halos, each 30,000 kilometers in diameter, were originally commissioned by Master Builder Faber and constructed by the [[guild]] of [[Bornstellar's father]] at the [[greater Ark]], the first Ark installation to be constructed. Only one of these original rings ultimately survived to be used in the Forerunners' final plan; this ring was designated [[Installation 07]]. Later on, an improved, separate array of six installations was constructed at the [[Installation 00|lesser Ark]],<ref>'''Halo: Cryptum''', ''page 329'' (''"Slowly it dawned on me that I was looking upon another array of installations: six rings, each rising from one of the petals of an enormous flower."'')</ref><ref name="s250">'''Halo: Silentium''', ''pages 250-251''</ref> although the construction of the second Ark and its more powerful Halos was delayed by the Council for some time to prevent the Builders from becoming too powerful.<ref>'''Halo: Silentium''', ''page 45''</ref>

[[File:Array.png|thumb|right|300px|Installation 00 sending the Halo Array through a [[slipspace portal]] during the [[Forerunner-Flood war]].]]

The seven Halos then remained relatively dormant for approximately one hundred thousand years, though at least [[Installation 05]] experienced a major Flood outbreak, while [[Installation 04]] was visited briefly by other species,<ref>''"[[Conversations from the Universe]]"''</ref> including a [[unidentified alien vessel|major crash-landing]] in [[40,000 BCE]].<ref>'''Halo: Combat Evolved Anniversary''', ''[[Terminal (Halo: Combat Evolved Anniversary)|Terminals 5-6]]''</ref>

[[File:H2A-AlphaHaloDestruction.jpg|250px|right|thumb|The destruction of Installation 04.]]

Eventually, the stellar coordinates of [[Installation 04]] were discovered through the combination of a [[Sigma Octanus IV artifact|crystal artifact]] on [[Sigma Octanus IV]] and a [[Babd Catha Forerunner vessel|huge Forerunner artifact]] buried under the surface of [[Reach]]. The coordinates were utilized by the {{UNSCShip|Pillar of Autumn}}'s shipboard [[AI]] [[Cortana]] to escape from the [[Fall of Reach]]. The cruiser arrived over the Installation's orbit and was subsequently shot down by Covenant ships. Most of the ship's combat personnel escaped and made landfall on the artificial construct, triggering the [[Battle of Installation 04]].  

During their investigations on Installation 04, the Covenant encountered a [[Flood containment facility]] and unknowingly released the dormant Flood; they quickly, but only partially, reestablished containment. Soon, a squad of [[UNSC Marine Corps|Marines]] led by [[Captain (Navy)|Captain]] [[Jacob Keyes]] accidentally broke quarantine again, expecting to find a large Covenant weapons cache. The human-waged guerrilla war quickly turned into a massive four-way battle between [[United Nations Space Command|UNSC]] forces, the Covenant, [[Sentinel]]s led by [[343 Guilty Spark]], and the Flood.  

Soon, 343 Guilty Spark, John-117, and [[Arbiter]] [[Thel 'Vadam]] discovered that the Ark had been constructing a [[Installation 08|new Installation 04]], to replace the one which had previously been destroyed. This new installation was only days from being completed. The humans decided to activate the new ring to stop the Flood, resulting in the incomplete ring destroying itself,<ref>'''[[Halo: The Essential Visual Guide]]''', ''page 14''</ref> severely damaging the Ark in the process.<ref name="hitd c2">'''Halo: Hunters in the Dark''', Chapter 2</ref>

[[File:HSS-Infinity-Halo.png|thumb|250px|{{UNSCShip|Infinity}} approaches a Halo installation.]]

By [[2553#January|January 2553]], the UNSC had begun an active search for the remaining Halo installations, with the intent to decommission them.<ref>'''Halo: Glasslands''', ''page 50''</ref> By at least [[2557|July 2557]], UNSC scientists were studying the Array for decommissioning, with facilities at Installations 03 and 05. Installation 00 was scouted by both automated probes and the ONI vessel {{UNSCShip|Rubicon}}, which was lost several days after its arrival due to the actions of [[343 Guilty Spark]].<ref>'''[[Halo: Primordium]]'''</ref>

[[Installation 07]] was discovered in early [[2555]] due to records found on [[Sarcophagus]] by Dr. [[Luther Mann]] with an ONI research group stationed on the ring immediately afterward. A crisis occurred when it was discovered that Installation 07 — as well as the other Halos — were counting down to activation in five weeks from March 8, 2555. As the stand-by failsafe protocol had never been deactivated, it was realized that the Ark was the only location where the Array could've been activated. With the help of [[Huragok]] [[Drifts Randomly]], the [[Portal at Voi]] was reactivated, but Earth came [[Invasion of Earth|under attack]] from [[Retriever Sentinel]]s from the Ark. A joint UNSC-[[Swords of Sanghelios]] [[Operation: FAR STORM|mission]] was launched to the Ark where it was discovered that the Ark's now-[[rampancy|rampant]] [[monitor]], [[000 Tragic Solitude]], had initiated the activation with the help of [[Bobby Kodiak]]. Having witnessed the destruction sentient life caused, particularly to Forerunner constructs, Tragic Solitude had activated the Array for a two-fold reason: to trick humanity into reactivating the portal so he could strip-mine Earth for materials to repair the Ark and eliminate the sentient species of the galaxy. Mann was able to deactivate the Array from the Ark and the team forced Tragic Solitude to end the Invasion of Earth. After Tragic Solitude attacked again, he was destroyed by Bobby Kodiak at the cost of his own life, ending the threat the rogue monitor posed to sentient life.<ref>'''[[Halo: Hunters in the Dark]]'''</ref> At some point following the loss of Installation 08, Installation 00 began to construct [[Installation 09|a new replacement]], one that would be maintained in the Ark's Foundry in a near-finished state for some time.<ref name="Hold the Line">'''[[Halo Wars 2]]''', campaign level ''[[Hold the Line]]''</ref>

In [[2556#February|February 2556]], the [[Outer Colony]] world of [[Sedra]] suffered a deadly [[bioweapon]] [[Terrorist attack on Sedra City|attack]] by [[Unidentified Sangheili Zealot (Sedra)|a Sangheili terrorist]]. The bioweapon source was traced to a new element mined from [[Alpha Shard|a surviving fragment]] of [[Installation 04]], created by the [[supernova]]-level explosion that had destroyed the original installation. A joint [[ONI]]-[[Sedran Colonial Guard]] [[Mission to Alpha Shard|mission]] was launched to capture the human smugglers mining the element and to destroy the deposits to prevent future use of the bioweapon. Though most of the team was killed, ONI [[Lieutenant Commander]] [[Jameson Locke]] and Sedran Private [[Talitha Macer]] escaped in the smugglers' {{Class|Bactrian|freighter}} while [[Colonel]] [[Randall Aiken]] sacrificed himself to destroy the deposits and the fragment's resident [[Lekgolo]] population with a [[HAVOK tactical nuclear weapon]].<ref>'''[[Halo: Nightfall]]'''</ref>

By early [[2557]], humanity had returned to the Ark and set up the [[Henry Lamb Research Outpost]]. Under the guidance of the [[smart AI]] [[Isabel]], the researchers began directing Retriever Sentinels to strip-mine lifeless systems to repair the Ark. The reconstruction slowly reached full automation until the humans were no longer needed to nudge it along. Over time, the Ark was repaired with noticeable differences between one day and the next over only the course of three months.<ref>'''[[Halo Wars 2]]''' - ''[[Phoenix Logs]]''</ref>

Later, the scientists studying Installation 03 located the [[Composer]] on the ring and accidentally activated it, causing them to [[mind transfer|become digitized]]. However, the sensor data left over from the incident led to the discovery of the [[shield world]] [[Requiem]]. Later, the [[Ur-Didact|Didact]] traveled to Ivanoff Station near Installation 03 to retrieve the Composer and used the device to harvest the essences of the entire research staff before heading for Earth.<ref>'''Halo 4'''</ref> Meanwhile, [[Jul 'Mdama's Covenant]] and their [[Promethean]] allies attempted to take control of Installation 03 by using the [[Conduit]] to open [[slipspace portal]]s across the ring, but the attack was repelled by a [[Spartan]] [[Headhunter]].<ref>'''Halo: Spartan Strike''', ''[[Operation C: Valiant Hammer]]''</ref>

A day later, after the Didact's [[New Phoenix Incident|defeat at Earth]], the Forerunner and some of his Promethean forces fell on Installation 03 via a slipspace portal. SPARTAN-II [[Blue Team]] followed, resulting in a [[Skirmish on Installation 03|a skirmish]] fought on both Installation 03 and the [[Composer's Forge]]. The Forge's monitor, [[859 Static Carillon]], transported Installation 03 over the Forge for the Didact, who intended to use the ring to finally destroy humanity.<ref name="HE9">'''Halo: Escalation''', ''[[Halo: Escalation Issue 9|Issue #9]]''</ref> However, the monitor instead allied with the Spartans due to his disagreements with the Didact and helped them defeat the Forerunner. After John-117 disabled the Halo's failsafes, Static Carillon ejected the segment housing the [[Control Room (Installation 03)|control room]], causing it to fall upon the Composer's Forge. The monitor then stabilized the ring and took it to an unknown location for repairs.<ref name="HE10">'''Halo: Escalation''', ''[[Halo: Escalation Issue 10|Issue #10]]''</ref>

In late [[2558]], Installation 00 became a battlefield once again as the mercenary organization known as the [[Banished]] arrived there following a sudden shutdown of the Earth portal. The Banished launched an assault on the UNSC bases on the Ark and soon gained control of the entire installation. In [[2559|May 2559]], the {{UNSCShip|Spirit of Fire}}, having drifted in space for 28 years, was mysteriously transported to Installation 00 by an agency evidently within the Ark.<ref>'''[[Halo Wars 2]]''', campaign level ''[[The Signal]]''</ref> During [[Second Ark Conflict|the ensuing conflict]] between the UNSC and the occupying Banished forces, Professor [[Ellen Anders]] learned of the contingency ring held within the Foundry and was able to launch the new Halo, with the intent of deploying it to Installation 04's former site in the [[Soell system]] where a [[distress beacon]] could be raised to the UNSC.{{Ref/Reuse|Hold the Line}} While the Halo was successfully sent through the portal, its firing mechanism disabled by Professor Anders, the ring was intercepted and forced out of slipspace on the way by a [[Guardian]].<ref name="Last Stand">'''[[Halo Wars 2]]''', campaign level ''[[Last Stand (Halo Wars 2 level)|Last Stand]]''</ref>

[[File:LoreStream_Halo_Scale_Comparison.png|left|thumb|250px|A scale comparison of the UNSC ''Infinity'' Mt. Rainier and a Halo Ring.]]

The Halos encountered in the modern times are 10,000 kilometers in diameter; this size is roughly similar to that of [[Earth]], which is 12,756&nbsp;km in diameter. While the original twelve Halos had a diameter of 30,000 kilometers,<ref>'''Halo: Cryptum''', ''page 310''</ref> concerns about their structural stability and transport led to the second series of rings being reduced in size.{{Ref/Reuse|maker}} The surface of each ring is 318 kilometers wide,<ref>'''Halo: The Essential Visual Guide''', ''page 6''</ref> with a depth of 22.3 kilometers<ref>'''Halo: The Fall of Reach''', ''page 339'' (2001)</ref><ref>'''Halo: The Flood''', ''page 13'' (2003)</ref> to 47 kilometers.{{Ref/Reuse|lorestream}}{{Ref/Note|The depth laid out in ''Halo: The Fall of Reach'' lists the ring's thickness as 22.3km, while the Lore Stream conducted by 343 Industries lists a depth of 47km. It is possible this disrepancy comes from the inclusion (or lack thereof) of the outer walls keeping the atmosphere in.}} The overall circumference of the ring is 31,415&nbsp;km and the interior surface area is 9,985,200&nbsp;km² - roughly the size of Canada.{{Ref/Reuse|lorestream}} The main structure of the ring is constructed of a superdense foundational material,<ref>'''Halo: The Flood''', ''page 340''</ref> with elaborate scaffolding and cantilever structures laid over it to support the artificial landmasses and the myriad tunnel networks and caverns that riddle the installation's internal structure.{{Ref/Reuse|halo3halo}} Many of these tunnels are transit conduits meant for use by the ring's Sentinels, though some of them can be traversed by humanoid beings.<ref>'''[[Halo: Combat Evolved]]''', campaign level ''[[Halo (Halo: Combat Evolved level)|Halo]]''</ref>

The Halo rings achieve their "gravity" through [[artificial gravity]] generators - despite their shape, the ring does not need to spin to create its gravitational pull, though they do spin for other reasons unrelated to gravity generation.{{Ref/Reuse|lorestream}} Due to this, the various [[Refugia]] present on the installation's surface may have different surface gravity, terrain, lighting and atmospheric conditions.{{Ref/Reuse|lorestream}} When the {{UNSCShip|Pillar of Autumn}} was detonated, it blasted a large mass from Installation 04; no longer a full loop, the centripetal force applied in much greater strength on the newly formed weak point, causing the ring to rip apart.<ref>'''Halo: Combat Evolved''' campaign level, ''[[The Maw]]''</ref>

The Halos are capable of repairing themselves to some degree, replacing damaged plates of foundation material and restoring biological sections.<ref>'''Halo: Primordium''', ''page 77-78''</ref> Some of the 30,000&nbsp;km-diameter Halos could also be reduced to a smaller size by shedding large portions of the foundation.{{Ref/Reuse|maker}} In order to prevent the ring from falling apart during this process, it could generate a hard light hub with spokes which hold each of the foundation plates in place.<ref>'''Halo: Primordium''', ''pages 345-346''</ref> However, the self-reduction process was far from perfect and made the original Halos prone to instability and collapse.{{Ref/Reuse|maker}} The newer Halos are capable of safely ejecting segments as well due to their modular and reconfigurable construction,{{Ref/Reuse|lorestream}} as long as the process is overseen by a capable enough intelligence such as a [[monitor]].{{Ref/Reuse|HE10}} Additionally, small, specifically defined parts of the Halos' terrain (along with the underlying foundation layers) can be jettisoned into space as a precautionary measure against Flood outbreaks.{{Ref/Reuse|Last Stand}}<ref name="cea t4">'''Halo: Combat Evolved Anniversary''', ''[[Terminal (Halo: Combat Evolved Anniversary)|Terminal Four]]''</ref> In time, the ecosystems of these ejected sections can be restored by the Halos' automated systems.{{Ref/Reuse|cea t4}}

Each installation in the final Halo Array orbits a large, dense planet—most commonly a gas giant—which serves as a gravitational anchor.{{Ref/Reuse|gas giants}}{{Ref/Reuse|lorestream}} For example, Installation 04 and Installation 05 orbited [[Threshold]] and [[Substance]], respectively, which are both large gas giants, while Installation 03 is anchored to a large rocky planet.{{Ref/Reuse|h4composer}}

[[File:343.JPG|right|thumb|250px|343 Guilty Spark, monitor of Installation 04.]]

The installations are designed to be run by advanced artificial intelligence constructs specially assigned by the Forerunners. The highest intelligence on each installation is a single monitor.<ref>'''Halo: Combat Evolved''', level ''[[343 Guilty Spark (level)|343 Guilty Spark]]''</ref> The monitor's task is to ensure that the installation's [[Sentinel]]s, which range from [[Constructor]]s to [[Sentinel Aggressor|Aggressors]] and [[Enforcer]]s, repair, maintain, and defend the ring from damage, contain Flood specimens, and ensure that their own installation is ready to fire on demand, including running activation simulations.{{Ref/Reuse|gravemind}} Monitors also have access to their respective installation's defensive system.<ref>'''Halo: Combat Evolved Anniversary''', ''Terminal 1''</ref>

An intricate layer of metallic panels is laid down several meters below the surface of the terrain, upon which rock, soil, and eventually vegetation is added. Slopes, hills and mountains can be created by sculpting these panels.{{Ref/Reuse|halo3halo}} Some features, such as landslides, are the result of time, and have been formed naturally. Others, such as the frigid conditions of the [[Quarantine Zone]] or the lake near the [[Temple (Installation 05)|Temple]] on [[Installation 05]] were artificially created.<ref>'''Halo 2''', campaign level ''[[Delta Halo]]''</ref> There are also numerous indigenous life-forms that live on the Halos; these were brought on the installations as part of the Lifeworkers' conservation project. The structures seen on the surface of the installations are built as part of the underlying structure, with the terrain then "printed" on top of them, creating the appearance of structures built into the surrounding landscape when the inverse is in fact true.{{Ref/Reuse|lorestream}}

[[File:AnniversaryControlRoom.png|thumb|right|250px|The [[Control Room]] of Installation 04.]]

Facilities of the Halo Array contain advanced [[teleportation grid]]s, allowing instantaneous transportation for a Monitor or Reclaimer to any place on the installation. Under normal circumstances, these grids cannot be accessed by the Flood, though the Gravemind was able to use that of Installation 05 by controlling [[2401 Penitent Tangent]].{{Ref/Reuse|gravemind}} For Sentinels, the installation is riddled with tunnel and cave networks for access and transportation.{{Ref/Reuse|Flood240}}

The Halo installations are also equipped with drive engines spaced along their rim.{{Ref/Reuse|lorestream}} In the event of an emergency, a Halo can maneuver itself to avoid damage from a collision or weaponry.<ref>'''Halo: Cryptum,''', ''page 314''</ref> While ideally moved through fixed [[slipspace portal|portals]], the rings are able to perform slipspace jumps under their own power. In the case of at least the original twelve rings, a failsafe measure implemented in the event of capture by hostile forces would transition the Halo into slipspace and place it on a collision course with a planet or other celestial body, ensuring the weapon's destruction rather than allowing it to fall in the wrong hands.<ref>'''Halo: Primordium''', ''pages 279, 339''</ref> At the moment of [[Installation 04]]'s destruction, at least [[Alpha Shard|one major fragment]] of the ring was moved into slipspace, likely as part of a similar failsafe.<ref name="wp shard">[https://www.halowaypoint.com/en-us/universe/locations/halo-ring-fragment '''Halo Waypoint''': ''Alpha Shard'']</ref>

When activated, the Halo rings release a burst of cross-phased supermassive neutrinos.{{Ref/Reuse|c274}} The burst possesses a harmonic frequency, which can be tuned to destroy the nervous system of any macroscopic organism that possesses one, even one as rudimentary as a notochord, as shown in the aftermath of a low-powered test firing of a Halo performed by [[Mendicant Bias]] in [[Charum Hakkor system|the system]] of Charum Hakkor. Fine tuning the pulse can also allow for selective extermination of lifeforms with varying degrees of neural complexity.<ref>[https://twitter.com/GrimBrotherOne/status/766840297498157056 '''Twitter''': ''Jeff Easterling on Twitter'']</ref> The Halo effect is able to target and eliminate most forms of neural structures, from biological nervous systems to esoteric [[neural physics]] constructs, although the effect does not extend to [[artificial intelligence]]s.<ref>'''Halo: Silentium''', ''page 310''</ref> Simpler life forms that do not possess a neural system, such as microbes, fungi, algae, mosses, and traditional plants are unaffected.<ref name="c131">'''Halo: Cryptum''', ''pages 131-133''</ref> While organisms aboard the twelve older rings were safe from the Halo effect itself due to its directional nature, any sentient being would still experience an uncomfortable sensation in the vicinity of the pulse.<ref>'''Halo: Silentium''', ''pages 272-273''</ref> Any living creature on the newer seven rings, however, would be killed and need to be reintroduced following the firing of the array.{{Ref/Reuse|lorestream}}

Halo Installations make use of [[Composer]] technology to an unknown degree as part of their firing.{{Ref/Reuse|lorestream}}

|[[Omega Halo]]

The installations in the neoteric{{Ref/Reuse|neoteric}} Halo Array are numbered in the order they were built in,{{Ref/Reuse|construction order}} while their alphabetical designations were assigned in the order in which they were fired, with [[Installation 04|Alpha Halo]] being the first ring to fire.<ref>''Halo: Silentium'', p. 327</ref> Although [[Installation 07]] was originally constructed as part of the first series of larger Halos, it was the last ring to be added to the neoteric Array while being heavily modified to suit its new role, hence the designation.<ref>[https://www.reddit.com/r/halo/comments/70wbxc/return_to_the_denomination_installation_04_b_c/dn76qup/ ''Reddit: Return to the denomination. Installation 04 (B), (C). Canonically. 343 PLS'' (comment by GrimBrotherOne)]</ref>

! style="width:50px;"  | Name

! style="width:100px;" | Location

! style="width:100px;" | Monitor

! style="width:100px;" | Status

|[[Orion Arm]]<ref name="WarfleetGalaxy">''[[Halo: Warfleet]]'', p. 12-13</ref>

|[[001]]

|[[Norma Arm]]{{Ref/Reuse|WarfleetGalaxy}}

|[[Khaphrae system]], [[Scutum-Centaurus Arm]]{{Ref/Reuse|WarfleetGalaxy}} {{C|formerly}}

|[[Perseus Arm]]{{Ref/Reuse|WarfleetGalaxy}}

|[[16807]]

|[[Sagittarius Arm]]{{Ref/Reuse|WarfleetGalaxy}}

|[[117649 Despondent Pyre]] ''(missing)''

! style="width:100px;" | Location

|Destroyed Over Installation 00

*The Halos are remarkably similar to the eponymous megastructure of [[Wikipedia:Larry Niven|Larry Niven's]] ''[[Wikipedia:Ringworld|Ringworld]]'' series. However, Niven's Ringworld encircles a large star, whereas the Halos merely orbit planets, being much smaller than the former. The Halos are also very similar to the [[Wikipedia:Orbital (The Culture)|Orbitals]] from [[Wikipedia:Iain M. Banks|Iain M. Banks']] ''Culture'' series, though considerably smaller.

*In a ''Halo: Combat Evolved'' [[Pre-Xbox Halo|prototype]], Installation 04 had a section that was only partially constructed. This feature was dropped from the final game, though it inspired the design of the second Installation 04.

== Gallery ==

File:H2A - ZenithRing.jpg|Installation 05 in ''[[Halo 2: Anniversary]]''.

File:H5G-LegendaryHalo.png|A Halo in ''[[Halo 5: Guardians]]''.

File:HM-Thanolekgolo.png|Alpha Shard in ''[[Halo Mythos]]''.

File:HW2-Halo.png|Captain [[James Cutter]] stands before Installation 04's second replacement in ''[[Halo Wars 2]]''.

File:FH4 - Halo Showcase Skybox.png|''[[The Halo Experience Showcase]]''<nowiki/>'s unique skybox featuring a Halo ring in ''Forza Horizon 4''.

File:HI E319 TheRingReveal.png|John-117 gazing at a destroyed Halo ring from the ''[[Halo Infinite]] [[Discover Hope]]'' trailer.

*''[[Halo: Evolutions - Essential Tales of the Halo Universe]]''

*''[[Halo 5: Guardians A Hero Falls trailer|A Hero Falls]]''

*''[[Halo Mythos]]''