Installation 04

''Installation 04 redirects here. For other uses, see Installation 04 (disambiguation)''

"Whoever controls Halo controls the fate of the universe."

- Captain Jacob Keyes

Installation 04, also known as Alpha Halo, or simply Halo, was one of seven ring-shaped superweapons that comprised the Forerunners' Halo Array.

The Covenant reverentially described Installation 04 as either the First Holy Ring or the First Sacred Ring. After its destruction at the end of the Battle of Installation 04, the Ark started to construct a replacement for Installation 04.

Overview
The purpose of Installation 04, along with its brethren, was to preclude and thwart the parasite forms known as the Flood from consuming all sentient life in the galaxy by destroying all sentient life to prevent eventual consumption. In the event of a Flood outbreak, one of the seven installations could be triggered (in turn triggering the remaining Halos) to annihilate all sentient life within a radius of 25,000 light years. In the event of an unexpected shutdown, all remaining rings would go into a "standby state", in which they could be fired at once from the Ark if need be.

Installation 04, until its destruction by John-117, was controlled by the Forerunner artificial intelligence construct (Monitor), 343 Guilty Spark.

The climate of Installation 04 was very similar to Earth's climate. There have been hurricanes over the oceans on the ring. The weather was, however, extremely unpredictable - rain and snowfall could occur at random, leading Cortana to wonder if the weather was intentionally irregular, or if it followed a pattern such as snow being deliberately made at the control room to slow the Flood. The ring boasted a diverse ecosystem, which included colonies of Thanolekgolo.

Installation 04 orbited the massive gas giant Threshold, and was suspended in the Lagrange point between Threshold and its largest natural satellite, Basis. The installation had a 24-degree axial tilt from Threshold's orbital plane. Due to this, any given point on the surface of the ring received sunlight from the star Soell for half of the time it was on the sunny side of Threshold, and none when was on the dark side. This created a somewhat unusual day-night cycle for the ring, in which it was dark three-fourths of the time and had no sunrise or sunset similar to those of a planet.

With a diameter of 10,000km and a surface width of 318km, the ring has a surface area of 9,990,000km2.

Construction and early history
The Forerunners had Installation 04 constructed by the Foundry of Installation 00 approximately around the same time as the rest of the Halo Array, circa 97,445 BCE during the Forerunner-Flood war. The array was designed by the Forerunner Builders to combat the parasitic Flood by eradicating them and all sentient life in the Milky Way. After the rings were built, Installation 04 and its fellow Halos were distributed from Installation 00 to positions across the galaxy through slipstream space portals.

When the IsoDidact activated the Array at the Forerunner-Flood war's conclusion, ending the centuries-long conflict, Installation 04 was the first to fire, followed shortly after by the other six Halo rings. Installation 04 lay dormant for a hundred thousand years, with 343 Guilty Spark and his Sentinels ready to keep the Flood confined in the Flood containment facilities and keeping the infrastructure of the Halo in perfect working order.

Intermediate period
After eons of uneventful existence on Installation 04, 343 Guilty Spark eventually found himself bored. For his own amusement, Spark began an experiment in which he evacuated entire sections of the Installation into space; according to Spark, these were experiments to measure the geologic effects of exposure to the vacuum of space and the eventual biological recovery of the evacuated sections, in order to gain insight into emergency response scenarios.

Around 40,000 BCE, an unidentified alien vessel crash landed in Sector 1215. Sometime prior to the crash the ship started broadcasting a distress signal. After attempting to translate it, 343 Guilty Spark blocked the signal, as no communication revealing the location of any of the Halos was allowed. After no lifeforms exited for several days, Spark had a large sarcophagus constructed around the vessel.

Between the activation of the Array and the arrival of the UNSC and the Covenant, a number of space-faring species stumbled across the installation. Although they reportedly explored the facility and recorded their findings, all of these species eventually left without breaking containment.

Discovery and destruction
"Halo... It's finished." "No, I think we're just getting started."

- Cortana and John-117 after the destruction of Installation 04.



The Covenant discovered the location of Installation 04 after the Covenant Fleet of Particular Justice followed the, which was fleeing from the Fall of Reach through slipspace. The Halos are deeply ingrained into the Covenant's religious dogma, but prior to this discovery they had never actually found one. Due to the Covenant's faster slipspace capabilities, they arrived before the Pillar of Autumn.

The Pillar of Autumn arrived around September 19, 2552 and was promptly shot down by the warding Covenant ships. Shortly thereafter, the Covenant ground forces on Installation 04 accidentally unleashed the Flood from captivity. Humans, Flood, and the Covenant fought massive battles against one another as the Forerunner constructs tried to control the outbreak by activating Halo. The ring's monitor, 343 Guilty Spark, tried to convince the Master Chief to activate Halo. Not knowing the truth of what it did, he attempted to light the ring but was stopped by his AI friend and companion Cortana who was in the Core. She informed the Master Chief of Halo's true purpose and stashed the Activation Index in her memory banks. The Monitor betrayed the two and tried to kill the Master Chief and retrieve Cortana, but the two escaped and started plotting against him.

In the conclusion of the battle, John-117 detonated the Pillar of Autumn ' s fusion reactors in order to destroy the ring. The explosion critically damaged the superstructure below it; the resulting shockwave and damage to the ring's systems destabilized the ring, shattering it into pieces.

Only a handful of humans and Covenant survived the battle. 343 Guilty Spark floated through space to a gas mining platform over Threshold, where he stumbled upon a Covenant expeditionary force. Inspired by his words, they began a heretical rebellion against the greater Covenant. Installation 04's destruction is seen as the first step in the chain of events that led to the Great Schism. The Heretics were quelled by Arbiter Thel 'Vadam who silenced their leader, but the seeds of a rebellion were planted. The Monitor was then captured by the loyal Covenant and later defected to the humans' side until he was destroyed on the replacement Alpha Halo by SPARTAN-117 with the help of Sergeant Johnson.

Installation 04 was the first Halo installation encountered by humanity, as well as first to be destroyed. Its destruction triggered the activation of a portal leading to Shield World 006 within Onyx, and also caused the Ark to start constructing a replacement ring.

Debris field
There is now a large field of debris where Installation 04 was, though a few large chunks of the ring remain. Some smaller pieces of Installation 04 have landed on Basis, while others have burned up in Threshold's atmosphere upon entry. One damaged fragment notably made a slipspace jump as a safety measure, and ended up in a distant system.

The Mona Lisa
Following the return of the survivors from the battle, the Office of Naval Intelligence learned of the Flood lifeform. Section III sought to establish a research laboratory in order to control the Flood parasite and possibly weaponize it against the Covenant. A science team headed by Major John Smith was authorized to take command of the prison vessel Mona Lisa. After bringing a group of Covenant prisoners aboard, they jumped to the wreckage of Alpha Halo in the Soell system. Some Flood specimens had survived the ringworld's destruction and were recovered to be experimented on both human and Covenant prisoners. However, the Flood soon broke quarantine and infected the ship. ONI later dispatched a prowler, the, to assess the status of the Mona Lisa under the pretenses of investigating Halo's debris field. On October 25, 2552, the prowler was forced to destroy the overrun vessel with a Shiva-class nuclear missile.

Replacement
Shortly after the destruction of the Halo, Installation 00 began to automatically construct a new Halo to replace Installation 04. This exact copy of the first Halo ring was nearing completion only a few months after the first ring was destroyed, but was also subsequently destroyed when it was fired before it was ready by the John-117 and Cortana. 343 Guilty Spark attempted to prevent this, but was finally destroyed by the Master Chief with the help of Sergeant Johnson in this new ring's Control Room. By 2559, the Ark had constructed another replacement Halo, which was launched by the crew of the in an attempt to use it as a signal buoy to contact the UNSC, but the ring was intercepted by the Created on its way to the Soell system.

Post-war
The UNSC's peace treaty with the Covenant forbids either party from landing on the remains of Installation 04.

Lost fragment
When the Pillar of Autumn ' s reactors went critical, Installation 04 attempted to activate a safety measure and make a slipspace jump. However, this self-preservation protocol was only partly successful, and only a small portion of the ring managed to enter slipspace before the Autumn ' s reactors overloaded and destroyed the ring. The surviving fragment of the Halo reentered normal space in the vicinity of a red giant star some distance away from the Orrichon system and was caught in the giant star's orbit. This fragment was home to a unique element apparently created by the heat of the ring's explosion and not found elsewhere in the universe. The element was later refined and used in a bioweapon unleashed in a terrorist attack on Sedra City. Alpha Shard was eventually destroyed after a classified mission.

Assessment of debris on Basis
Sometimes after the war, UNSC Spartan-IV operatives were sent on a reconnaissance mission to Basis. They used for the first time the VECTOR-class Mjolnir armor, built from Covenant Luminary-related technologies and designed for artifact retrieval. Their covert mission was to assess the debris of Alpha Halo scattered on the moon's surface.

Redesigns
While the design of the Halos has stayed largely consistent across all post-Halo: Combat Evolved media, Installation 04 underwent a significant visual overhaul in Halo: Combat Evolved Anniversary. The entire superstructure of the ring has been redesigned. To wit, the surface features are completely different and much more pronounced, including additions such as rows of prominent prongs lining the ring's edges and large-scale patterns of bluish light, in contrast to the more subdued original design in which the features on the outer surface appear largely flat due to the immense scale of the ring. This redesign has not been carried over to post-Anniversary media: the prongs are absent from Installation 03 in Halo 4, and a visual allusion to the Halos in Halo 4: Forward Unto Dawn follows the original design.

In Halo 2: Anniversary, Installation 04 has received some visual changes (including prominent blue lighting in the circular patterns on the ring's outer surface) but is otherwise closer to the original version than the Halo: Combat Evolved Anniversary redesign. Curiously, Installation 05 in the same game uses a distinct model, which is noticeably wider than the Installation 04 one and bears different surface patterning. Furthermore, Blur Studio used Installation 05's model, rather than that of the original Installation 04, from Halo 2 Anniversary for Installation 04C in Halo Wars 2.

Miscellaneous

 * Sergeant Johnson humorously describes Installation 04 as "God's own anti-son-of-a-bitch-machine" and a "giant hula-hoop".
 * Except for Boarding Action and Chiron TL-34, all Halo: Combat Evolved multiplayer maps are set on Installation 04.
 * It is possible to see falling debris from Installation 04 on the map Burial Mounds.

List of appearances

 * Halo: The Fall of Reach
 * Halo: Combat Evolved
 * Halo: The Flood
 * Halo: First Strike
 * Halo 2
 * Conversations from the Universe
 * Halo Graphic Novel
 * The Last Voyage of the Infinite Succor
 * Breaking Quarantine
 * Halo: Ghosts of Onyx
 * Halo 3
 * Halo Legends
 * Origins
 * Halo: Evolutions - Essential Tales of the Halo Universe
 * The Mona Lisa
 * ''Halo: Reach
 * Halo: Fall of Reach
 * Invasion
 * Halo: Combat Evolved Anniversary
 * Terminals
 * Halo 4
 * Halo: Silentium
 * Halo: Escalation
 * Halo: Broken Circle
 * Halo: Nightfall
 * Halo 2: Anniversary
 * Terminals
 * Halo: Hunters in the Dark
 * Halo 5: Guardians
 * Halo Mythos
 * Halo: Tales from Slipspace
 * Dominion Splinter
 * Halo Wars 2