Installation 07

Installation 07, also known as Zeta Halo, is one of the seven rings in the Halo Array. Unlike the other six remaining Halo installations, which were constructed as a separate array of rings with the diameter of 10,000 kilometers, Installation 07 is the only surviving ring from the original main array of twelve 30,000-kilometer-wide Halos. However, the installation's diameter was reduced to 10,000 kilometers after most of its superstructure was discarded as a result of heavy damage.

Construction and commissioning
Unlike the other six rings in the final Halo Array, Installation 07 was manufactured at the greater Ark instead of Installation 00 or the "lesser Ark". As a result, it was originally three times the size of a normal Halo ring (30,000 kilometers in diameter). Like the other Halos, Installation 07 served a secondary purpose as a Lifeworker preserve for biological specimens from across the galaxy as part of the Conservation Measure. Installation 07 was primarily dedicated to humans, being home to various species and subspecies of the human genus, alongside numerous fauna and flora. The humans living on the installation identified themselves as Tudejsa, meaning "the People" or "People from Here". In the beginning, these humans were allowed to build their own societies and were mostly left undisturbed by the Forerunners. Some of the People even managed to construct rudimentary cities.

During the Forerunner-Flood war, Master Builder Faber placed Installation 07, along with the other eleven rings in the original Array, under control of the Contender-class AI Mendicant Bias, and one of the primary extensions of the AI was placed on the ring. At one point, the Master Builder broke his deal with the Librarian and began to use the human specimens on the ring for his brutal experiments on the Flood. Some of the Lifeworkers serving on the installation complied and aided Faber's minions in these experiments, while those most loyal to the Librarian worked to keep the installation's biological preserves intact. Faber also forcibly drafted Warrior-Servants as an additional security force for the installation. In their exhaustive experiments, the Master Builder's researchers found that the majority of humans were apparently immune to the Flood, which they believed to be a result of a "cure" developed by early humanity during the ancient human-Flood conflict. In reality, no cure ever existed and the humans' apparent immunity was the result of the Flood's ongoing strategy to target Forerunners only.

Faber's researchers believed that a cure to the Flood might be found via extracting ancestral memory imprints from humans who carried the Librarian's special geas. Since the human specimens on the installation lacked these imprints, Faber, against the instructions of the Librarian and the Ecumene Council, ordered his forces to gather humans from the Librarian's special population on Earth and transplant them to Installation 07. Consequently, both the installation's own human specimens and humans from Earth would be used in the Master Builder's experiments, in what the humans came to know as the "Palace of Pain"; however, the "palace" was not in fact a single location as the humans believed, but many Flood research facilities across the ring, most of them being re-purposed Lifeworker biological research stations.

Under new management
Circa 100,043 BCE, around sixty years after Faber had begun his unsanctioned experiments, he charged Mendicant Bias with test-firing Installation 07 in Charum Hakkor's star system. As an unprecedented side-effect of this firing, the Primordial, an entity that had been imprisoned on the planet for millennia–in fact a Gravemind left behind by the Precursors–was released from its near-impervious cell. The Primordial, or the Captive as it was known to the Forerunners, was then taken on the ring by order of the Master Builder. Lifeworkers in the employ of the Master Builder studied the creature, but remained unsure as to its true nature - while some believed it to be related to the Flood, others did not.

Not trusting the Lifeworkers, Faber assigned Mendicant Bias to interrogate the Primordial, which, using its knowledge of the Precursors' plan and compelling arguments that the Forerunners' rule led to eternal stagnation, eventually managed to turn the AI against its Forerunner masters. The creature also managed to manipulate the Master Builder into complying it with its schemes; whether Faber was fully aware of the Primordial's goals, or simply an uninformed pawn, is unclear. The Primordial then took charge of operations on Installation 07, encouraging the Master Builder to continue his experiments on humans, apparently for no reason other than its own amusement.

The Master Builder himself departed the installation shortly after the Primordial had been brought in, leaving his researchers in charge. Over time, Faber reduced the role of Lifeworkers on the installation, eventually confining them to smaller preserves with select groups of humans, while his minions continued their attempts to infect humans. As Faber's researchers took more and more humans from across the ring for their experiments, many human societies effectively collapsed; the People abandoned the cities out of fear that the Forerunners would come take them away, escaping to the wilderness.

After Mendicant Bias had been subverted by the Primordial, the AI broke the safeguards in the ring's various Flood containment facilities, allowing the parasite to spread to various sections of the installation. The Flood devoured large areas of the Halo's artificial landscape, covering it with Flood biomass. As more and more Forerunners succumbed to the Flood across the installation, the Master Builder had a machine known as the Composer used to stave off the effects of Flood infection in a number of infected Forerunners.

Crisis
After Installation 07 had been officially considered missing for 43 years, the Master Builder had the ring transported to the primary San 'Shyuum world Janjur Qom and authorized its activation to suppress a rebellion, wiping out all but few of the San 'Shyuum. However, he failed to foresee the consequences of this decision. Immediately following the firing, many of the Warrior-Servants and Lifeworkers assigned to serve under Faber's Builder forces openly rebelled against the Master Builder, viewing his actions as a grave offense against the Mantle. This rebellion was, for the most part, violently suppressed by Faber's Builder Security forces and the remaining Warriors and Lifeworkers were given a choice to either serve Faber or be killed. Some chose to ally with the Master Builder while those loyal to the Council continued to resist, sabotaging power stations and other facilities in an attempt to cripple the installation from within.

Once the news of Faber's use of the installation against the San 'Shyuum reached the Ecumene Council, Faber was arrested and put to trial in the Forerunner capital. The other eleven Halo rings were gathered in orbit over the capital, while Installation 07 remained missing after the incident at Janjur Qom.

Battle of the capital
During Faber's trial, Installation 07 appeared over the capital. The rampant Mendicant Bias managed to subvert its other extensions on five of the remaining Halo rings, and cripple the capital's forces, while releasing the Master Builder from captivity. However, the emergent Bornstellar-Didact used a control code to temporarily stun Mendicant Bias, which allowed the capital's defenses to respond to the attack and assault the Halos under Mendicant Bias' control. The capital's fleets opened fire on Installation 07, while the Halo's sentinels and the Master Builder's ships attempted to defend it. Many of the ships involved in the battle were destroyed and crashed across the ringworld. Despite the installation taking heavy damage, Mendicant Bias successfully activated the ring's main weapon at the conclusion of the battle, presumably wiping out all life in the capital system.

Refuge
Following the battle at the capital, Installation 07 retreated into a slipspace portal, reappearing in a distant star system near the galaxy's edges. This was part of a security measure beyond Mendicant Bias' control – in order to prevent the ring from falling in the wrong hands, it had been programmed to enter a course which would result in a collision with a planet in several days. As the primary, automated control systems had been sabotaged, the Primordial and Mendicant Bias were unable to direct the Halo's movements. Instead, they began to gather humans in a last-ditch effort to use them to manually steer the ring away from its destructive course.

After its successful retreat, Installation 07 began automated measures to repair the damage it had taken. Over the next few days, entire plates of the ring's superstructure were replaced and rebuilt. However, the installation was still low on power due to many of the power stations being down, and entire sections kept experiencing power outages. Meanwhile, the Halo's human and Forerunner occupants were caught amidst the chaos. Mendicant Bias used its all-encompassing control to corrupt most ancillas and Forerunner armors on the ring, turning the armors into death-traps for their wearers. This forced Forerunners on the installation to remove their armor in order to survive.

The Lifeworker beacons across the installation, used to transmit orders to the local humans via their geas, were giving conflicting commands which kept changing as the various factions fought for control of the beacons. Similar beacons were used to transmit orders to Lifeworkers and their ancillas across the ring, and although they believed the orders came from the Librarian, there was no definite certainty of this. Acting under these orders, a Lifeworker known as Genemender Folder of Fortune extracted and stored the consciousnesses and ancient personality imprints of any humans he found, doing the same to himself, believing it would save him from having to serve the Master Builder.

During the battle above the capital, two Earth humans, Chakas and Riser, who had been captured by Faber and were aboard ships headed to Installation 07, crashed in different parts of the ring. Chakas landed near a village, where a young woman known as Vinnevra found him and later took him to see her grandfather, Gamelpar, who had been brought on the ring from Earth by Faber's minions long ago. The group then proceeded to travel under the guidance of Vinnevra's geas, which had activated upon Chakas' arrival, but upon arriving at the destination, they discovered it to be a "Palace of Pain", where the Primordial itself and a number of war sphinxes were herding numerous humans inside. After traveling in the opposite direction for several days, the group reunited with Riser, who had landed in a Flood-infested region nearby. Eventually, they came across a rail transport which brought them to Lifeworker Central, where a monitor instructed them to enter another transport.

Salvage effort
The humans were then taken to the facility where Mendicant Bias' core was housed. There, humans from Earth were separated from the Tudejsa, and their ancestral personality imprints were removed by Mendicant Bias and the Primordial. They were given a choice to cooperate with Mendicant Bias and have their revenge against the Forerunners for destroying their civilization ten thousand years earlier; however, they would first have to help save the Halo from colliding with the approaching planet. Those who accepted Bias' offer were sent to various control stations spread out across the Halo, including the Cartographer. However, humans alone did not possess the knowledge necessary to properly interface with the ring; instead, Flood-infected Forerunners processed by the Composer were brought in and connected with each human to the Halo's control systems. As Installation 07 approached the planet, the controllers successfully managed to reorient the ring in a way the planet would pass through the center; this way, the ring would take heavy damage but had a chance of surviving.

Despite this, there was still a grave risk that the gravitational pull of the planet would tear the Halo apart. Plates of foundation material were moved over the exterior walls in preparation for repairs during the passage. Sentinels and other craft were positioned across the Halo, firing their engines in an attempt to alter the installation's course, with little success. The Halo's central hard light hub and spokes, typically used in the activation process of the main weapon, were activated to slow down the ring's passage over the planet, and to borrow some of the planet's velocity in order to alter the ring's orbit in an effort to prevent collisions in possible future orbital passes. However, the hard-light structures did not last long against the planet's surface, disintegrating shortly after the impact. The installation's outer walls quickly exceeded their capacity to manage the strain of the planet's tidal stresses, coming apart at various points. As the walls gave way, the foundational plates began to bend and distort, with massive gaps–some of them hundreds of kilometers in diameter–opening between them.

Retake and reduction
While the installation had already begun its passage, a fleet led by the IsoDidact appeared, and the Didact used his control codes to shut Mendicant Bias down. He immediately entered the Cartographer and connected to the installation's controls with Chakas, while dreadnoughts from the Didact's fleet moved to provide power via connections across the ring. Despite the additional power supply, the Halo could not be saved in its entirety. In order to relieve the tidal stresses exerted on the Halo, the Didact ordered that the installation be reduced by discarding the most damaged plates; this would also allow repairs to be made at the lesser Ark. To preserve the most important sections, they were locked into slipspace stasis, effectively rendering them invulnerable to damage from the outside. After the passage of the planet, the ring's central hub and spokes were activated to act as support braces for the intact sections while two-thirds of the superstructure was shed into space, contracting the Halo to a diameter of 10,000 kilometers. On its remaining power, the installation generated a slipspace portal and transitioned to the greater Ark.

Aftermath
Most of the Installation's surviving biological specimens, including humans, were saved by the Lifeworkers and relocated to the Ark. Mendicant Bias' core on the installation was deactivated, while the AI itself was forced to undergo a process to "correct" its rampancy. The Primordial was captured and placed in a cage within a chamber deep underneath the installation's surface; there, the Didact interrogated the being with an injured Chakas, before executing it. The majority of the Flood, including ten inactive proto-Graveminds and the infected Forerunners processed by the Composer, remained on the ring, watched over by a number of remaining monitors. By order of the Didact, the Halo, now shrouded in perpetual cloud, was eventually sent through a slipspace portal, to remain as a memorial, a "sacred tomb" for the millions of beings that had died there.

At the conclusion of the Forerunner-Flood war, Installation 07 was activated, along with the other six rings in the final Halo Array, wiping out all life within its effective radius of 25,000 light years.

Activation
On November 3, 2552, during the Battle of Installation 05, a signal was sent to this Halo from Installation 05, putting the former - as well as the entire array - on standby mode. Installation 07 was then ready to fire on demand.

Deactivation and later history
Later the same year, during the Battle of Installation 00, Installation 07 was still on standby. However, SPARTAN John-117 deactivated the Halo Array before it could be fired, rendering Installation 07 inert.

By June 2557, the Office of Naval Intelligence had managed to perform a cursory examination of Installation 07, discovering its size and deducing that its surface was overrun by a perpetual cloud cover, although information on the ring remained sparse. The cloud-covered surface led an ONI scientist to speculate on whether the ring's life support systems had never recovered from the damage it sustained 100,000 years prior. As of 2558, Sangheili implemented adequate containment and sterilization protocols within possible Flood infected zones on the installation. The Sangheili then informed the UNSC of its contamination efforts. Human and Sangheili naval forces soon began monitoring the installation, ensuring there is no possible way for the Flood to escape.

Trivia
The installation's surface, as portrayed in the Halo 3 texture, resembles Venus' surface.

List of appearances

 * Halo 2 (Holographic representation)
 * Halo 3 (Holographic representation)
 * Halo: Legends
 * Origins
 * Halo: Cryptum
 * Halo: Combat Evolved Anniversary
 * Terminals
 * Halo: Primordium
 * Halo: Silentium
 * Halo: Rebirth