Installation 05

"This installation has a successful utilization record of 1.2 trillion simulated and one actual. It is ready to fire on demand."

- 2401 Penitent Tangent

Installation 05, also known as Delta Halo, is one of the massive Halo fortress worlds built by the Forerunners. The ring, monitored by 2401 Penitent Tangent, orbits a gas giant known as Substance in the Coelest system. Installation 05 was the third Halo discovered by humanity and second found by the Covenant, it became a battleground near the end of the Human-Covenant War; more importantly, it was at Installation 05 that the Great Schism, the civil war that sundered the Covenant, began. The installation was ultimately glassed in order to prevent the Flood from escaping in the wake of the Battle of Installation 05.

Overview
The purpose of Installation 05, along with its brethren, was to preclude and thwart the parasite forms known as the Flood from consuming all sentient life in the galaxy. In the event of a Flood outbreak, one of the seven installations could be triggered to annihilate all sentient life within 25,000 light years. Once one ring is set off all remaining rings would activate. All seven rings could be fired at once if need be.

The climate of Installation 05 is similar to that of Installation 04, with varying weather conditions in different areas. Its terrain includes lakes and jungles, as well as the ice and snow-filled Quarantine Zone.

Architecture
"You know, I think the Forerunners built these new structures around the old, to protect them, to honor them."

- Cortana, commenting on some of the structures on Delta Halo.

The architecture of structures on Installation 05 follows the general Forerunner aesthetic (i.e angular design, and same basic functional structures), but has a clearly distinct style from some other installations such as Installation 00 or 04, an example being Installation 05's Control Room having similarity to Installation 04's Control Room in purpose, but with a different look, including a spherical shape at the center of the building. This is different from both versions of Installation 04, which look almost exactly the same (being of the same style), and have the same surroundings. In addition, many structures on Installation 05, including the temple, appear to be more weathered than those on other installations, having a slightly brown-tinted gray color as opposed to the clean, pristine silver-gray surface material of most Forerunner structures.

Much of the decor within the structures of Installation 05 seems to be less practical and more ostentatious than that of Installation 04. Many of the rooms contain standing tables and basins that seem to serve a purely aesthetic purpose, perhaps at one time serving as lamps or torches.

A curious feature on Installation 05 are the stone ruins encountered on the ring. While visibly consistent with Forerunner architecture, the ruins seem clearly older and more primitive than most Forerunner structures, and seemingly predate the construction of the ring. They are also made of stone, as opposed to the metallic material seen on the majority of Forerunner constructs. This brings up the question of whether these are Forerunner structures at all, or if they were built by an even more ancient civilization or the Forerunners themselves long time before the construction of the Halo installations, and later moved to the ring for unknown reasons. Still, only a fraction of the installation's structures represent the older variety, as most of them are in a similar condition as on other known installations. Some of the newer structures were also built around the older ones to support and protect them, which is clearly evident in some of the spires built over the lake near the temple.

Forerunner stone ruins are not exclusive to Installation 05, however. The Temple of the Abiding Truth in Ontom, Sanghelios, as well as a complex of ruins in a desert in an unspecified location, held similar structures. Much like some of the ruins on Installation 05, the desert ruin complex is also surrounded by newer structures.

Locations

 * "Bastion of the Brutes"
 * Control Room
 * Flood research facility
 * Library
 * Quarantine Zone
 * Sentinel Wall
 * Temple

History
"Those who built this place knew what they wrought. Do not mistake their intent, or all will perish as they did before."

- Gravemind

It is assumed that Installation 05 was built around the same time as the rest of the Halo Array, circa 101,000 years before the events of 2552. It was activated by the Forerunners at the conclusion of the Forerunner-Flood war, eradicating all sentient life in the galaxy and, presumably, destroying the Flood as well, with the exception of those specimens kept in the Halos for research. After the Array was fired, the installation was hardly peaceful, with over 32,967 simulated test firing a day. As of 2552, it had a record of 1.2 trillion simulated firings and one actual activation.

Flood outbreak
Around the year 97,227 BCE, the Flood on Installation 05 escaped and evaded containment due to negligence on the part of the installation's Monitor, Penitent Tangent. The Flood quickly grew out of control around the area of the Installation's Library. The Flood were kept contained by a Sentinel Wall built around the Library, but 2401 Penitent Tangent was captured. Without it, the Sentinels of the Halo lacked a controlling intelligence and so many of the structures around Installation 05 fell into disrepair, and most of the Installation came to look like a jungle strewn with ruins.

Somehow, the Flood on the ring were able to amass enough biomass to create a Gravemind, and at the time of the Human-Covenant war, it was holding 2401 Penitent Tangent captive. Even with the addition of Forerunner Aggressor Sentinels and Enforcers, the Flood were able to remain loose, albeit contained within the Quarantine Zone by the Sentinel Wall. This stalemate is believed to be the cause of the slow decline into the horrible condition of the structures of the Installation. The Gravemind itself resided in the chamber directly below the Index Chamber in the center of the Library.

Discovery
In 2552, the High Prophet of Regret discovered the location of Installation 05 during the Battle of Earth. He made a slipspace jump from Earth to the Installation, followed closely by Commander Miranda Keyes' ship.

After evaluating their situation, Keyes ordered John-117 to capture and interrogate the Prophet of Regret about the Installation. After fighting the Covenant in various locations, John-117 and Cortana overheard Regret talking about activating the Installation which, according to the High Prophet, would start the "Great Journey". Keyes then ordered John-117 to locate and eliminate Regret, while she and her Marines aboard the In Amber Clad proceed towards the Library of the Installation to retrieve the Index, both operations aimed to prevent the High Prophet from activating the Installation.

After fighting hordes of Covenant forces, John-117 finally located Regret in a huge temple over a crater lake. John-117 successfully eliminated the High Prophet and proceeded to be exfiltrated. However, at the same time, the Covenant's holy city, High Charity, arrived and sent Regret's personal CAS-class assault carrier to destroy the temple. John-117 escaped the destruction by jumping off into the crater lake, only to be captured by the Gravemind.

The battle
After the Covenant had arrived, the Prophet of Truth ordered the Arbiter Thel 'Vadamee to go on the Installation's surface and retrieve the sacred icon to enable the start of the Great Journey. On the surface, the Arbiter was tasked by the Jiralhanae Chieftain, Tartarus, to shutdown the Sentinel Wall to allow Covenant forces to be deployed and assist the cause.

The Arbiter then proceeded beyond the Wall, only to be troubled with the Flood throughout his journey in the Quarantine Zone to the Installation's Library, and later assisted by Rtas 'Vadumee and his officers. In the Library, the Arbiter assaulted Commander Miranda Keyes and Sgt. Johnson. After neutralizing the pair, the Arbiter retrieved the Index but was later betrayed and cast into the depths of the Index Chamber by Tartarus who acted under the orders of the High Prophets.

The Arbiter was then saved by the Gravemind from death and brought to a chamber where the Gravemind rests. Within the chamber, the Arbiter met John-117, the infected High Prophet of Regret, 2401 Penitent Tangent and the Gravemind. The five proceeded into the discussion of Halo's true purpose. Through the Installation's teleportation grid, the Gravemind sent John-117 to High Charity, and the Arbiter to the Installation's Control Center to search for the Index and prevent it from activating the Halo Array.

After navigating throughout the whole of High Charity, the Flood-infected and controlled In Amber Clad made a slipspace jump inside the Covenant holy city and crashed into one of the Covenant structures. It was apparent that the Flood had successfully penetrated the Covenant's defenses and managed to spread its infection throughout the whole city. Fighting his way through the Flood and Covenant forces, John-117 found himself unsuccessful in retrieving the Index. The Jiralhanae Chieftain Tartarus and the High Prophet of Truth, along with Miranda Keyes and Johnson held captive, left the site while leaving the High Prophet of Mercy being infected slowly by an Infection form. Cortana instructed John-117 to hunt down the Prophet of Truth while she began the detonation of In Amber Clad's engines to prevent the activation of Halo.

At the same time, the Arbiter managed to gather enough Sangheili and Unggoy support to engage on the Jiralhanae and the Kig-Yar. He met Rtas 'Vadum once again on a cliff overlooking the Control Center, with Tartarus arriving shortly at the entrance of the Control Center, Index and Commander Keyes in hand. The Arbiter, assisted by Rtas 'Vadum, rallied more Sangheili and Unggoy to support their operation to take over and commandeer a Scarab. The Arbiter 'rescued' Johnson from his captors and agreed to escort him in a Banshee to the Control Center. Johnson, piloting the Scarab, destroyed the entrance of the Control Center, allowing the Arbiter to enter the structure.

Simultaneously, John-117 was sent into the Forerunner Dreadnought to follow the Prophet of Truth by Cortana using the power conduit. Cortana, left behind, faced Gravemind who had gained complete control over High Charity. Meanwhile, in space over the Installation, the Defense Fleet of High Charity commanded by Sangheili and Jiralhanae shipmasters engaged one another as a result of the expanded Civil War of the Covenant. With the threat of the Flood escaping the Installation, both sides focused a small number of their ships to the burning of any ships trying to escape Halo.

The Arbiter delayed the activation of the Installation with the help of Johnson. Impatient and unsatisfied with the heresy told by the Arbiter, Tartarus enabled the firing sequence and engaged the Arbiter. The Arbiter successfully killed the Jiralhanae Chieftain with the support of Johnson and Miranda Keyes and hastily pulled the Index out of its chamber. The firing sequence was put on standby mode, ready for remote activation through the Ark.

At the end of the battle, High Charity had been overrun by the Flood. Battles between Jiralhanae-led loyalist forces and Sangheili-led separatist forces began in orbit. Soon, the Flood began attempting to board ships in low orbit, forcing the factions to target them and prevent further infestation. After defeating most of the straggling Jiralhanae ships, the remnants of the Sangheili fleet sterilized the installation by glassing its surface, thereby preventing the Flood from leaving the Coelest system.

Post-war
After the end of the Human-Covenant War, the Office of Naval Intelligence established Lisbon Station in orbit of Installation 05. The station's purpose was to study the Halo prior to its decommissioning. At some point, unusual activity on the ring was investigated by ONI through remote surveying technology. The intelligence agency discovered strange structures that suddenly appeared on the installation's surface at key power and data junctions. ONI created a War Games simulation based off of these structures for SPARTAN-IVs to train in, with the intent to send these Spartans to Installation 05 to examine the structures. The Spartans were trained to deal with any possible threat from Aggressor Sentinels, Promethean constructs, or Covenant remnants that would interfere with the investigation. It was later discovered that, around these structures, the local Aggressor Sentinel suddenly became actively hostile and organized.

Trivia

 * There are six Halo 2 campaign levels that take place on Installation 05: Delta Halo, Regret, Sacred Icon, Quarantine Zone, Uprising, and The Great Journey.
 * The Halo 2 multiplayer maps set on Installation 05 include Ascension, Backwash, Desolation, Lockout, Relic, Sanctuary, Uplift and Warlock. Meanwhile, the Halo 3 multiplayer map Cold Storage is the only one in Halo 3 to be set on Installation 05.

Gallery
 File:Delta Halo.jpg|A view of Installation 05. File:Halo6.jpg|A Phantom approaches Delta Halo. File:PT2401.JPG|The Monitor of Installation 05, 2401 Penitent Tangent. File:Sacredicon1600.jpg|The Library of Installation 05. File:Argodaemon-DeltaHaloTank-1600-1200.jpg|A structure and a bridge on Installation 05. File:Uprising.jpg|The control room of Installation 05. File:Control Room3.jpg|Another view of the installation's control center. File:H2 - Delta Halo view.png|The temple structure on Installation 05. File:H2 - Delta Halo towers 1.png|A pair of towers framing older stone ruins on the lake surrounding the temple. File:QZ - battle zone 1.png|The dilapidated conditions of the installation's Quarantine Zone. File:H2-Uprising_Eld.png|An iteration of the ubiquitous Eld symbol found on Installation 05. File:H2-Uprising_mural.png|A mural in a structure on the installation, identical to a design at Installation 04's Silent Cartographer. File:H2 ringbirds.jpg|Quadwings on Delta Halo. File:Coldstorage1 inline.jpg|A compromised Flood containment facility deep within Installation 05. File:43472886-Full.jpg|A section of Installation 05 completely overrun by the Flood. File:Installation 05.jpg|Installation 05's firing sequence being canceled in Halo 2. File:Coelest.jpg|A measurement of Substance and Installation 05 from space. File:Haloverse-PlanetDistances scaled.jpg|A scaling of the distance between Installation 04, Threshold and its moon Basis within the Soell system at the top, as well as a scaling of the distance between Substance and Installation 05 within Coelest system at the bottom. File:H2A - DeltaHalo Scenery.jpg|Scenery on Delta Halo from Halo 2 Anniversary. File:H2A - Temple.jpg|The Temple as it appears in Halo 2 Anniversary. 

List of appearances

 * Halo 2
 * Halo 3
 * Halo Legends
 * Origins
 * Halo: Combat Evolved Anniversary
 * Terminals
 * Halo 4
 * Halo: Broken Circle
 * Halo 2 Anniversary
 * Terminals
 * Halo 5: Guardians (Simulation only)