Halo Alpha
Halo Alpha

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Cortana, what exactly am I looking at?”
— Commander Miranda Keyes
“That… is another Halo.”
— Cortana

Installation 05, also known as Delta Halo to humanity, is one of the seven massive Halo fortress worlds built by the Forerunners. It is also the third Halo installation to be discovered by Humanity. Installation 05 orbits the gas giant Substance in the Coelest system, and was managed by its Monitor, 2401 Penitent Tangent.


The purpose of Installation 05, along with its brethren, was to preclude and stop 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.


“This installation has a successful utilization record of 1.2 trillion simulated and one actual. It is ready to fire on demand.”It is assumed that Installation 05 was built around the same time as Installation 04, circa 100,000 years before the events of 2552. It was activated shortly thereafter by the Forerunners, 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. As of 2552, it had a record of 1.2 trillion simulated firings and one actual activation. At some point after the ring's construction, a monument was erected on a secluded island. It was dedicated to the Warrior-Servants who fought in the final siege of Forerunner colonies by prehistoric humans.[2]

Flood Outbreak[]

Coldstorage1 inline

A Forerunner structure deep in Installation 05.

About 200 years prior to 2552, the Flood on Installation 05 escaped and evaded containment due to negligence on the part of the installation's Monitor, Penitent Tangent.[3] 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 horrible conditions, and most of the Installation came to look like a jungle strewn with ruins.

At the time of the Human-Covenant War, a Gravemind was holding 2401 Penitent Tangent captive. Even with the addition of Forerunner Sentinel Majors 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. A battle record has been shown on:


LF.Xx.3273 research and containment facility; [delta site] has experienced catastrophic specimen containment failure. All apertures into the facility will be locked until further notice. Atmosphere evacuation and [reduction of ambient temperature] protocols have already been enacted. Request maintenance and security detail [at earliest opportunity]. [8 minutes] elapsed since initial containment failure. REPORT: CONTAINMENT FAILURE

Waiting for maintenance and security detail. [32 minutes, 9 seconds] elapsed since request. REPORT: CONTAINMENT FAILURE

Still waiting for maintenance and security detail. [24 hours] elapsed since request. REPORT: SECURITY BREACH

LF.Xx.3273 research and containment facility; [delta site] has experienced a security breach via emergency [slip stream space] transportation conduits. Emergency [slip stream space] transportation conduits have been placed in recursive mode to contain unauthorized hostile life forms. Request emergency security detail. Still waiting for primary maintenance and security detail. [2512332 hours, 14 minutes, 6 seconds]elapsed since initial request.


2401 [PENITENT TANGENT] has been lax in the areas of maintenance and security.


LF.Xx.3273 research and containment facility [alpha, beta, gamma, epsilon, zeta, and kappa sites] have all replied [systems normal] within expected constraints. This would tend to signify that the containment failure was purely mechanical in nature; perhaps a manufacturing flaw. As no [outside agent] has accessed [delta site] in the past [874068942 hours, 4 minutes, 46 seconds]—[allowing for a 61360-hour, 54, minute, 2-second margin of error]—sabotage would seem unlikely.


LF.Xx.3273 research and containment facility; [delta site] is currently being held at [.01 atm] / [184K]. Local maintenance and security hubs have failed to reply within expected constraints. [Bumping maintenance and security request up] to [quadrant oversight].


LF.Xx.3273 research and containment facility; [delta site] is currently being held at [1 atm] / [278K] as atmospheric seals were showing signs of stress. [Quadrant oversight] has failed to reply within expected constraints. [Bumping maintenance and security request all the way up] to 2401 [PENITENT TANGENT].


LF.Xx.3273 research and containment facility; [delta site] emergency [slip stream space] transportation conduits have been accessed by unauthorized parties.


2401 [PENITENT TANGENT], monitor of Installation 05, has been lax in the areas of maintenance and security. Requests for aid in said areas have gone unanswered by both 2401 and [subservient] systems well beyond expected constraints.


H2a 4

The discovery of Installation 05.

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 UNSC In Amber Clad.

After evaluating their situation, Miranda 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 a Covenant CCS-class battlecruiser 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[]

Installation05 FailedFiring

Installation 05's firing sequence being cancelled.

Main article: Battle of Installation 05

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 shut down 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, both of which to search for the Index and prevent it from activating the Halo Array. The Arbiter's presence sparked the start of the Great Schism, a civil war which would soon split the Covenant into the Loyalist and the Separatist.

After navigating throughout the whole of High Charity, the 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 begins 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 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. 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.

At the same time, 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.[4] 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 hastily pulled the Index out of its chamber. The firing sequence was put on standby mode, ready for remote activation through the Ark.


When Installation 05 was last seen, the Flood were seen having complete control over High Charity and several ships of the surrounding fleet, one of which would break through quarantine and eventually arrive at Earth. The Great Schism, a civil war between Covenant species, split the empire into Loyalist and Separatist factions. After the battle, the Sangheili fleet glassed the surface of Installation 05 to prevent any further escapes by the Flood.[1] The hologram in the Citadel on Installation 00 shows Installation 05's surface as completely barren.[5] After the Human-Covenant war, UNSC Infinity would establish Lisbon Station to study what was left of the ring and recover useful artifacts.[1][6]


“You know... I think the Forerunners built these new structures around the old, to protect them, honor them.”
Cortana, commenting on some of the structures on Delta Halo.[7]
H2A DeltaHalo1

Ruins on Installation 05.

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.

A curious feature on Installation 05 is some of its ruins. While visibly consistent with Forerunner architecture, the ruins seem clearly older and more primitive than most Forerunner structures. 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.[8] 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. It has also been suggested that some of the newer structures were built around the older ones to support and protect them.[7]

Forerunner stone ruins are not exclusive to Installation 05 however. A complex of ruins in an unknown location holds similar structures. Much like some of the ruins on Installation 05, this ruin complex is also surrounded by newer structures.



  • 2401 Penitent Tangent was the first known Monitor to be captured by the Flood.
  • The Halo 3 Multiplayer map Cold Storage is present on Installation 05.
  • There are six Halo 2 levels that take place on Installation 05; Delta Halo, Regret, Sacred Icon, Quarantine Zone, Uprising, and Great Journey.
  • When the control room of Installation 05 shoots a bolt of energy into the ball of energy at the center of halo, the bolt fired by the control room is visible, even though Halo is 10,000 km in diameter. As the control room is only a few km wide at most, the bolt was probably shown to be much bigger to be actually visible during the halting of the firing of halo, but a more likely answer to this is that the shot fired from the control room last, was charging in mid-air.
  • Like all Halo Arrays, Installation 05 gets its power from the Power Rooms which are connected to other Power Rooms placed around the whole ring. 


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