Battle of Installation 05

"Miranda Keyes"

The Battle of Installation 05, also known as the battle for the Second Ring of the Gods among the Covenant, was a major engagement in early November 2552 between the Covenant, the Flood, and the United Nations Space Command, with the aid of Forerunner Sentinels and those loyal to the Arbiter on the Forerunner ringworld Installation 05, otherwise known as "Delta Halo".

The battle saw the splintering of the Covenant empire as the Great Schism began, and the formation of an alliance between humanity and the Sangheili of the Fleet of Retribution, led by Thel 'Vadam and Rtas 'Vadum.

Prelude
In 97,227 BCE, 343 Guilty Spark—monitor of Installation 04—warned the monitor of Installation 05—2401 Penitent Tangent—of a pending outbreak in one the installation's Flood containment facilities. However, Penitent Tangent ignored the warning, and those that followed, for millennia. The installation's sentinels managed to keep the Flood largely contained in the Quarantine Zone around the Library, although the machines never managed to fully destroy the infestation. Eventually, a Gravemind formed on the installation and captured Penitent Tangent.

At the beginning of the Battle of Earth in October 20, 2552, the Prophet of Regret led Fleet of Sacred Consecration, which contained two s and thirteen s on an expeditionary raid that stumbled upon Earth, humanity's homeworld and the UNSC's strongest fortress. After substantial ground, air, and space losses, and faced with the possibility of being overrun on the ground and intercepted by UNSC ships if it tried to escape to orbit, Regret ordered a retreat. With Regret aboard, Solemn Penance made an emergency in-atmosphere slipspace jump over New Mombasa, with the  following it into slipspace.

At Fleet Admiral Lord Terrence Hood's order,, , , and were sent to follow and assist the In Amber Clad with the heavy assault carrier, as they were the closest, fastest UNSC ships to the carrier with charged slipspace capacitors. The ships intended to find out where the assault carrier was heading, or destroy the ship entirely to kill Regret. Their shadowing, however, was not exactingly precise. Only the frigate In Amber Clad successfully trailed the assault carrier to its destination. Dusk, a prowler, arrived a day later near the Covenant holy city of High Charity. While Coral Sea and Redoubtable conducted scans of Delta Halo's surface, the fate of the Paris is unknown.

Opening actions
On November 2, 2552, Solemn Penance exited slipspace over Installation 05, orbiting Substance in the Coelest system. Regret's assault carrier took position over the installation, establishing a solid ground presence with armor and patrols of Type-26 Banshees, and also companies of infantry by means of Type-52 Phantoms. The Covenant ground forces fortified themselves in a series of Forerunner ruins and temple structures, establishing anti-air defenses.

Meanwhile, In Amber Clad trailed behind and Commander Miranda Keyes, captain of In Amber Clad, ordered a platoon of Orbital Drop Shock Troopers and John-117 to establish a landing zone near a series of ruins and temples on Installation 05 to allow Sergeant Major Avery Johnson to bring in two D77-TC Pelicans to further expand the UNSC presence. The frigate made a quick pass-over of a segment of the ringworld, deploying a dozen SOEIV pods. Most survived the atmospheric insertion to the surface of the ring, but only four personnel eventually survived to make landfall—John-117 and three ODSTs. However, before they could land in the ruins, they were detected by the Covenant. Upon landing, SPARTAN-117 led the ODSTs in eliminating Covenant Shades and holding their position against waves of Covenant troops until a Pelican could drop off a M12 Warthog LRV and a pair of Marines. Although a major objective for John-117 and the Marines was to capture or assassinate the Prophet of Regret, the most important UNSC objective was to prevent the Covenant from activating the installation to fulfill what they would later learn to be the supposed Great Journey. To do this, UNSC forces had to infiltrate the Library, retrieve the activation index to prevent the Covenant from using it to activate Installation 05.

After Cortana translated a sermon from the Prophet of Regret, the UNSC became aware that the Covenant was intending to activate Installation 05. Regret's elimination became the primary objective for John-117, as his death would destabilize the Covenant politically and religiously. John-117 and a pair of Marines battled through a pair of Covenant-held temples before reaching an open platform. At the time, the Covenant became aware of UNSC activity and became increasingly aggressive, so Commander Keyes sent several Pelicans towards John-117, which air-dropped more resupply canisters on the platform. The UNSC continued their attack, proceeding from the platform to an anti-gravity gondola which took John-117 and his remaining Marines to a heavily-defended Forerunner underwater temple with a heavy Covenant presence. After emerging from the submerged temple at a hilly Forerunner ruin, they were engaged by more Covenant infantry reinforced by Phantoms attempting to halt the UNSC advance.

Assassination of Regret
However, the Covenant were ultimately unsuccessful. The UNSC succeeded in clearing a landing zone and more Marines were deployed to assist John-117 in reaching the temple the Prophet of Regret was located in. The UNSC forces commandeered an anti-gravity gondola, and despite being attacked by Covenant Type-26 Banshees and Sangheili Rangers, they were able to gain access to the main temple. After destroying several defense turrets, they entered the temple as the Prophet of Regret was finishing his sermon. Regret transmitted an apology to the Prophet of Truth, asking for forgiveness for his rash actions at Earth and for aid at the new installation. Truth, with the Prophet of Mercy's advice, reluctantly sent a large portion of the Covenant fleet to Installation 05 to retrieve the Hierarch. Shortly after, High Charity reverted from slipspace over Installation 05, along with the hundreds of warships of the High Charity defense fleet and the Second Fleet of Homogeneous Clarity. Responding to a distress signal from Regret, Special Operations Commander Rtas 'Vadumee planned to storm the temple by Phantom dropships in an urgent measure to kill John-117 and defend the Hierarch. However, the treacherous Prophet of Truth ultimately diverted the Phantoms, deliberately allowing the SPARTAN-II to kill Regret as part of his socio-political plans for the Covenant.

A large contingent of Sangheili Honor Guardsmen and Unggoy defended the Prophet, but John-117 was able to board the Prophet's gravity throne and beat the Prophet to death. During the fray, all the remaining Marines were presumably killed. Shortly thereafter, Solemn Penance repositioned over the main temple, and destroyed it with its energy projector. John-117 fell into the lake with seconds to spare and was grasped by the tentacles of the Gravemind, a Flood compound intelligence, and taken prisoner.

The containment shield
The Hierarchs' confidence in the abilities of the Sangheili Honor Guardsmen declined when the Prophet of Regret's bodyguards failed to save him from death at the hands of John-117. As a result, the High Prophets of Truth and Mercy ordered the Sangheili to step down as the protectors of the Prophets. In their place, the Jiralhanae filled in the void left by the disgraced Sangheili. Soon, the UNSC and the Covenant both raced to reach Installation 05's Library and seize the activation index. The UNSC wanted to keep it safe to prevent the activation of the installation, but the Covenant desired to bring the "Sacred Icon"—the Covenant name of the index—to the Control Room of the ring and activate the ring.

Before either faction could reach the Library, it was shielded by the containment shield—a recognized impenetrable energy shield denying anyone access to the Library. The shield was projected by a Forerunner power generator buried within a Sentinel wall, a large Forerunner complex heavily defended by various types of Sentinels, including Aggressors and Enforcers. Numbers of Jiralhanae, Kig-Yar, and Unggoy had attempted to penetrate the Sentinel wall, but they were all overwhelmed by Sentinel defenders. However, Arbiter Thel 'Vadamee was air-dropped by Chieftain of the Jiralhanae Tartarus's Phantom at the periphery of the wall in the beginning phase of a Covenant offensive to deactivate the containment shield, enter the Library, and seize the Sacred Icon. Eventually, the Arbiter battled his way through the area and deactivated the shield. However, there was a rampant Flood infestation: the second half of the Sentinel wall became heavily saturated with Flood forms, and the Flood soon began to outnumber the Sentinel defenders. Tartarus attempted to pick up the Arbiter in his Phantom and head directly for the Library, but his dropship was engaged by an Enforcer, forcing the Arbiter to battle through the warring Flood and Sentinels that resided in the Flood-infested wall by himself.

However, the Arbiter was not alone—the UNSC had dispatched a squad of Marines to also fight through the facility, but they were overwhelmed by the Flood, leaving a trail of crumpled bodies throughout the facility and fueling the Flood's ever-growing army. The Covenant apparently sent a small team of three Special Operations Sangheili to clear out the lower levels of the complex, but these too were killed. Finally, the Arbiter managed to exit from the Sentinel wall and enter the battle-torn icy plains of the Quarantine Zone.

Battle of the Quarantine Zone
"We shall cut into the heart of this infestation, retrieve the icon, and burn any Flood that stand in our way! Forward, warriors, and fear not pain or death!"

- Rtas 'Vadumee

The Quarantine Zone was intended to be a location where the Sentinel custodians of the installation could herd the Flood, and prevent them from entering the Library. Two Sentinel manufacturing facility ships hung in the air, deploying Sentinel reinforcements. However, the Quarantine Zone was compromised by the Flood, and the Flood managed to crash one of the floating facilities using a Type-26 Wraith, sending it plummeting down to the installation's surface.

The Arbiter met with Commander Rtas 'Vadumee and two other Sangheili just outside of the Sentinel wall, and together, they defended a small hill from the Flood before pushing inwards, where the Special Operations Commander had established a small outpost. There, the Special Operations force held out against waves of Flood attacks from the cliffs before they were reinforced by a pair of Phantoms that dropped off a Type-46 Spectre and a pair of Type-32 Ghosts. The Covenant were able to use these vehicles to advance through a large indoor Forerunner facility before entering the first of a series of expansive outdoor arctic canyons. Despite the prowess of the Special Operations Sangheili and the Arbiter, the UNSC were swifter to advance through the Quarantine Zone—In Amber Clad deployed a Pelican dropship that cruised above the battling Flood and Sentinels, cutting directly towards the Library while the Arbiter and his men were forced to fight through waves of Flood, including Flood and the vehicles they had commandeered, while all the while, Enforcers rained heavy fire.

The small Covenant task force was forced to debark from its vehicles as they transgressed the wreckage of one of the Sentinel constructor factories, although just beyond the wreckage on the other side, they were met by another Covenant Phantom, this one dropping off a Spectre manned by Rtas 'Vadumee himself and another Special Operations Sangheili. However, as they progressed through the last series of snowy plains, they were met with increasingly heavy resistance as they neared the Library. The Sentinels were in much larger force, while a large number of Flood-infested humans savagely held a barricade against the Library, using crates, turrets, and heavy weapons to prevent anyone to gain entrance to the Library and retrieve the index, which would eventually lead to the extermination of the Flood.

The Library
"The release of the parasite was unexpected, unfortunate. But, there is no need to panic. In truth, this is a time to rejoice. A moment that all the Covenant should savor... for the Sacred Icon has been found. With it, our path is clear, our entry into the Divine Beyond guaranteed! The Great Journey is nigh... and nothing, not even the Flood, can stop it!"

- Prophet of Truth

A small UNSC Marine force led by Miranda Keyes and Avery Johnson was able to slip past the Flood infestation into the Library, followed shortly by the Arbiter, Rtas 'Vadumee, and half a dozen Special Operations Sangheili. There were a pair of anti-gravity gondolas, that when activated, autonomously brought their passengers into the upper tiers of the Library, where the index was kept. While the UNSC was first able to seize a gondola, the Covenant were close behind. However, when the Flood began to screech, alerting the Covenant that they were in full force in the bowels of the Library, Rtas 'Vadumee took a pair of Special Operations Sangheili, holding them at the entrance to the gondolas to defend the rest from the Flood as the Arbiter took four Special Operations Sangheili on the second gondola, trailing behind the UNSC-held one. Flood entered the gondolas, jumping from the upper levels and also crawling in underneath on their undersides, assailing both the UNSC troops and the Sangheili forces. Tartarus, in his Phantom, attempted to provide cover fire for the Arbiter, using the three plasma cannons of his dropship to burn off any Flood on the upper levels of the Arbiter's gondola, but later, Tartarus chased after the UNSC-held gondola.

Finally, both gondolas ascended to the top levels of the Library, although the UNSC one arrived first, and a small UNSC force of six soldiers, led by Miranda Keyes and Avery Johnson, entered. Although many Flood combat forms had been exhausted in the Gravemind's last-ditch attempt to stave off the gondolas, there were a large number of Flood infection forms prowling the Library which killed off the four UNSC Marines as Keyes and Johnson advanced towards the core of the Library. Meanwhile, the Arbiter silently snuck in behind them. Miranda managed to grab the index over a seemingly endless chasm. Once Keyes and Johnson had the index, they were ambushed by Thel 'Vadamee. Johnson was knocked unconscious by the Arbiter, but Keyes was able to take down Arbiter's shields by firing at him with a M7 SMG. However, Tartarus entered with four of his Jiralhanae Captains. Tartarus used the Fist of Rukt to stun Miranda and gravitationally levitate her towards him, draping her over his shoulder and then clasping the index and securing it for himself. Tartarus informed Thel about the Jiralhanae's intended genocide of the increasingly incompetent Sangheili, an act sanctioned by the High Prophets themselves. The Chieftain then knocked the stunned Arbiter into a pit leading to the depths of Installation 05, initiating the Great Schism.

The engagement at the Library proved to be devastating to the UNSC and resulted in the loss of In Amber Clad as the Flood took over the frigate. Meanwhile, Tartarus brought the Sacred Icon to High Charity, where the Prophet of Truth exulted him and encouraged the Covenant to celebrate, for the Sacred Icon was secure, and that soon afterward, the Halos would be fired and the Great Journey would be brought upon the Covenant.

The Great Schism
"The Elites have failed to protect the Prophets, and in doing so, have put all our lives at risk. Let no warrior forget his oath, 'Thou, in faith, shall keep us safe, whilst we find the Path'. With my blessing, the Brutes now lead our fleets! They ask for your allegiance, and you shall give it."

- Prophet of Truth

The Covenant would not activate the Halos unimpeded. The Flood, who would be starved if the rings were activated, would soon attack the Covenant to prevent the activation, and the UNSC, who understood that all sentient life would be erased, also opposed the Covenant. Later, after the fragmentation of the Covenant into the Sangheili-dominated faction and the Prophet-led Covenant, the Sangheili would understand the true purpose of Halo and attack the Covenant to prevent them from activating the ringworld. Meanwhile, John-117, who had fallen into the lake, and the Arbiter, who had been thrust into the chasm of the Library, were both caught by the tentacles of the Gravemind, along with the assimilated Prophet of Regret and 2401 Penitent Tangent, the monitor of Installation 05. The Gravemind sent the Arbiter and John-117 to aid in his plan to prevent the activation of Installation 05, manipulating the Halo's teleportation grid to send John-117 to High Charity to search for the index, and sending the Arbiter to the cliffs just beyond the Control Room, another likely spot.

The Covenant's betrayal of the Sangheili led to a large-scale civil war on High Charity. The Covenant politico-military fractures were not restricted to High Charity: they extended to military units across the Covenant, including those on the surface of Installation 05. Upon Truth's order that the Jiralhanae were now the ruling caste of the Covenant, Tartarus ordered the execution of the Sangheili Councilors, who had been gathered in the Control Room of Installation 05 for the consecration of the Sacred Icon before the Halos were fired. While most of the Councilors were murdered in cold blood by Jiralhanae led by Captain Melchus, a small number were taken prisoner.

However, the Sangheili were quick to strike back. The Gravemind teleported the Arbiter to a high cliff near the Control Room, and gave him an objective: to prevent Tartarus from using the Sacred Icon and activating Halo, which would not result in the promised sublimation event of the Prophets, but only death and destruction on a galactic scale. The Arbiter arrived just too late, witnessing the murders of a handful of Sangheili from afar at the hands of the Jiralhanae, but was able to push forward against a number of patrolling Jiralhanae, and meet up with a number of surviving Sangheili warriors. The small group of survivors, led by the Arbiter, pushed northward through a large Jiralhanae-held Forerunner structure, unpinning small groups of scattered loyal Unggoy and killing dozens of Jiralhanae, Kig-Yar, and Yanme'e. Afterward, they emerged from the structure, and fought their way past several Jiralhanae camps, commandeering several Ghosts along the way. As they neared another cluster of structures, they encountered heavier resistance in the form of Jiralhanae-controlled Wraiths. The Arbiter and his Sangheili allies managed to defeat the Jiralhanae and secure a landing zone, allowing for additional Sangheili reinforcements to arrive.

After securing the first half of the camp, the Arbiter and his allies moved into the weapons cache, where the Jiralhanae had aggregated a large number of Covenant and UNSC weapons alike. The Arbiter led his group outside the structure and into a tunnel and defeated the Jiralhanae within. After exiting the tunnel, the Arbiter met with Rtas 'Vadumee who was commandeering a Wraith.

Fall of High Charity
"Now is the time of our unworlding, in a moment we shall all become...as gods. If you will falter, know this...one final effort is all that remains."

- The Prophet of Truth inspiring his loyalists to defeat the Flood on High Charity

John-117 was teleported by the Gravemind directly into the High Council Chamber of High Charity, where the Prophets of Truth and Mercy addressed the Covenant that the Sacred Icon was secure. Before the Spartan could kill both Prophets, they escaped by means of an elevator, while the doors were locked and waves of Jiralhanae Honor Guardsmen, Jiralhanae Minors, and Unggoy entered in an attempt to kill the supersoldier. Cortana managed to unlock the doors, and John-117 chased through two towers and a set of corridors in pursuit of Truth and Mercy. However, Cortana had discovered Marines that were being kept prisoner on High Charity and John-117 freed them. Truth's transmissions to the rest of the Covenant allowed Cortana to triangulate his position, allowing her to direct John-117 and the Marines in their hunt for the Prophet. The Covenant attempted to stop Cortana, but were unsuccessful.

As John-117 and the Marines reached Hanging Gardens A, the first scene of Covenant fratricide was seen, as Sangheili Honor Guards, Sangheili Minors, Mgalekgolo, and Unggoy fought against Jiralhanae and Kig-Yar Snipers amongst the massive plants. John-117 and his men advanced to the Mid Tower, where Rangers and Special Operations Sangheili entered the fray, and numerous Yanme'e entered the engagement. During the fight, the Flood-controlled In Amber Clad then jumped directly into High Charity, where it plummeted uncontrollably, crashing into the Far Tower. However, by the time that the small UNSC squad entered Hanging Gardens B, Sangheili resistance on High Charity had broken. In the second Hanging Gardens, the Sangheili and those loyal to them fell back, leaving behind large numbers of stationary shield generators, abandoning numbers of Unggoy to berserk Jiralhanae as the Sangheili fell back to the Far Tower and the Mausoleum of the Arbiter, drawing a last line of defense there. Despite their efforts, the Prophets of Truth and Mercy, Tartarus, and a handful of Jiralhanae Captains were able to tunnel through the last Sangheili defenses to the far docking bays of the Far Tower. John-117 pursued Tartarus, fighting through the Far Tower and the Mausoleum of the Arbiter to make it through to the landing pads. "The Great Journey waits for no one, brother... not even you."

- Truth betraying Mercy

The Spartan was too late, however. The Prophet of Truth ordered Tartarus to deliver the activation index to the Control Room of Installation 05, and activate the Halos. Tartarus took a detachment of Jiralhanae Honor Guards along with him in two Phantoms, along with UNSC prisoners Avery Johnson and Miranda Keyes. Truth and Mercy took a third Phantom to the Forerunner Dreadnought—the central energy source of High Charity, and also a fully functional Forerunner keyship that the two remaining High Prophets were going to use to reach Earth, and finish the battle. Meanwhile, the Flood were escaping from the crashed hulk of In Amber Clad. They seeped out of the rents in its hull armor and commandeered its Pelican dropships, sending them over the surface of High Charity, crashing into the floors and releasing combat forms, and spilling infection forms out of the air from opened hatches. The Prophet of Mercy was beset by an infection form and died before he could reach his Phantom. However, Tartarus and Truth were able to depart before John-117 could arrive.

"Cortana"

- John-117

By that time, resistance by the Sangheili and their allies had completely shattered on High Charity. There were few Sangheili or Mgalekgolo remaining, and only a few scattered Unggoy. The forces loyal to the Prophets, however, retained a large number of Jiralhanae, Kig-Yar, and Yanme'e. Despite the lack of a Sangheili ground force, they were still very much present in space, where the Covenant fleets over High Charity had splintered in allegiances, with Sangheili and Jiralhanae ships actively engaging and destroying each other. While Truth was taking a Phantom to the Forerunner ship, Cortana detected an energy conduit to the ship located in the Mausoleum tower ahead of John-117's position. John-117 entered the Mausoleum tower from the dropship landing pads, and engaged numerous Flood and Covenant hostiles. The Spartan eventually took a gravity lift to access the Sanctum of the Hierarchs. While John engaged Covenant forces, large numbers of Flood began to attack and the Spartan was forced to enter the energy conduit to reach the Forerunner ship. John-117 was able to jump in the conduit just in time, barely making it to the ship before it lifted off for Earth. However, Cortana stayed behind while John would attempt to neutralize the ship before it rallied the Covenant fleets at Earth. In the event that Tartarus was about to trigger the Halo Array, Cortana announced that she would detonate the fusion reactors of In Amber Clad—just like she had done to the at Installation 04—and the blast would destabilize the ring and prevent the activation of the Halos.

Shortly afterward, all Covenant resistance on High Charity broke and succumbed to the Flood, who had infested a large area of the planetoid even during the raging combat between the Covenant and the Flood. Cortana, who resided in High Charity's computer systems to be ready to detonate the frigate's reactors as a final fail-safe, was captured and interrogated by the Gravemind.

Assault on the Bastion of the Brutes
"Listen, you don't like me and I sure as hell don't like you. But if we don't do something, Mr. Mohawk's gonna activate this ring. And we're all gonna die."

- Avery Johnson to Thel 'Vadamee

Meanwhile, Rtas 'Vadumee informed the Arbiter that Tartarus was within the Control Room, and would soon be activating the Halos. However, the doors to the Control Room were nearly completely impenetrable, and would only be opened by the firing of the main cannon of a Type-47 Scarab walker. Fortunately, a Scarab was available at the Bastion of the Brutes, a Forerunner structure used by the Jiralhanae as their local base of operations.

While Rtas 'Vadumee advanced forward in a Wraith tank, the Arbiter and another Special Operations Sangheili took a Spectre, and together, the Sangheili battled through a swarm of Ghosts, several Wraiths, and a bombarding Phantom. Eventually, the Sangheili secured entrance into the Bastion of the Brutes, where the Arbiter found another Special Operations Sangheili and a pair of Mgalekgolo, all of whom were loyal to the Sangheili. Meanwhile, Rtas 'Vadumee said that he would briefly watch the Arbiter's back, and would prevent any Jiralhanae reinforcements from entering in behind them while they cleared out the stronghold. Later, he announced that he would retake the that was hanging in the distance. The Arbiter and his band of Sangheili and Mgalekgolo stormed the Bastion, fighting their way past Jiralhanae, Kig-Yar, Yanme'e, and even a Phantom. Eventually, they freed imprisoned Councilors and Mgalekgolo and eventually reached the platform where the Scarab was docked. Much to their surprise, they discovered the presence of humans who were being held prisoner by the Jiralhanae. Amongst the prisoners was Sergeant Avery Johnson. The Jiralhanae had just received orders from Tartarus to execute the prisoners, when the Arbiter and his followers attacked. The humans, with the help of their Sangheili allies-to-be, took advantage of this distraction to free themselves and take control of the Scarab.

After all the Jiralhanae on the platform were dead, there was a brief standoff between the Sangheili and the UNSC personnel. However, both the Arbiter and Sergeant Johnson realized that they shared a common enemy and objective. The two sides begrudgingly joined forces and set out to stop Tartarus from activating Halo.

The Control Room
"No Arbiter! The Great Journey has begun, and the Brutes, not the Elites, shall be the Prophets' escort!"

- Tartarus to Thel 'Vadamee

The Arbiter took possession of a Banshee and provided cover fire for Johnson's Scarab. Together, they fought their way past a large Jiralhanae force consisting of multiple Wraiths, Banshees, Spectres, and Shade turrets. Eventually, the group reached the Control Room and destroyed its doors with the Scarab's primary cannon. Inside the chamber, the Arbiter fought his way through numerous Jiralhanae forces who had been ordered to prevent the Arbiter from disturbing Tartarus while he activated the Halos. Despite reinforcements, the high-ranked Jiralhanae were unable to hold the room, and the Arbiter continued down an arched corridor before confronting Tartarus in the control room. Inside, he found Tartarus and several Jiralhanae, along with two prisoners—Miranda Keyes and 343 Guilty Spark who had been captured by the Covenant during the raid on the Threshold gas mine.

Tartarus had been trying to force Keyes to insert the index into its place, as only a Reclaimer could activate Halo. The Arbiter entered the control room and told the Chieftain to stand down. Tartarus refused, and his Jiralhanae were about to attack the Arbiter, when Johnson suddenly appeared, pointing a Type-50 particle beam rifle at Tartarus' head. Seeing that he was in danger, Tartarus ordered his Jiralhanae to hold back for the moment. The Arbiter then had Guilty Spark explain that the Halos were weapons of mass destruction, built by the Forerunners as a last resort means to stop the Flood. Spark further revealed the Forerunners ultimately perished when they activated the Halo Array, sacrificing themselves to contain the Flood. Despite Guilty Spark's revelations, Tartarus — blinded by his loyalty to the Prophets and his hatred for the Sangheili — refused to listen. The Chieftain threw Guilty Spark at Johnson, knocking him out for a moment. He then physically forced the Sacred Icon into Miranda Keyes' hand and shoved it into the receptacle, beginning the activation of Installation 05. Miranda jumped out of the way of the imminent firefight as the Arbiter, the conscious Johnson, and a small cluster of recently-arrived Sangheili Zealots and Councilors, charged at Tartarus and his guard of four Jiralhanae Captains. The Jiralhanae guards were quickly slain, and Tartarus retreated onto the three-level structure at the center of the control room. When the Arbiter and his allied Zealots and Councilors pursued, they found to their dismay that Tartarus was protected by a nearly impenetrable energy shield. Only Sergeant Johnson, with his particle beam rifle, could disable Tartarus' shields, and only for a few seconds.

Meanwhile, Miranda Keyes argued with Guilty Spark and eventually forced him to reveal that the firing sequence could be stopped if the Reclaimer simply removed the index from the its position. However, she could not do anything while Tartarus was still alive. The Arbiter and Sangheili battled Tartarus, who used his massive gravity hammer, the Fist of Rukt, to slay many high-ranking Sangheili. Eventually, the Arbiter succeeded in killing Tartarus. Commander Keyes immediately leapt to action after Tartarus died, snatching the index from the control panel. Despite the fact that Installation 05 was primed to fire, the removal of the index only triggered a partial firing, one that was inconsequential and led to the loss of no life whatsoever. However, 343 Guilty Spark informed them that because of the partial activation of Installation 05, the other five remaining installations were set onto standby mode, and were ready to fire upon command from a central Forerunner installation: the Ark.

Final space battle
Despite the isolated Sangheili ground victory on Installation 05, there was a much greater threat: the Flood. Having assumed dominance over the whole of High Charity and certain locations on Installation 05, they tried boldly expanding into space, attempting to take over Covenant warships. The ambitious Sangheili Major Voro 'Mantakree assumed command of the Incorruptible after mutinying against and killing his insane commander, Tano 'Inanraree, and audaciously sent a fleetwide dispatch to the idling Covenant fleet amassed over High Charity: the Flood were lifting off from Installation 05 in Type-25 Spirit dropships and Banshees, and were attempting to attack and take control of Covenant warships to spread throughout the galaxy. The fleets were united after the transmission, and four Covenant destroyers, including the Rapturous Arc, that were about to be consumed by the Flood were burned and destroyed to prevent the parasite from capturing the warships.

Shortly afterward, however, the fleets splintered without a common foe. The Jiralhanae Chieftain Gargantum attempted to coordinate a Jiralhanae uprising against the Sangheili, and chased after 'Mantakree with four Covenant frigate. Using deft tactics and maneuvering out the Sangheili carrier Lawgiver, the Incorruptible destroyed the Jiralhanae-controlled frigate Tenebrous, although the three remaining frigates, including Gargantum's personal frigate, the Twilight Compunction, continued pursuing him. Soon afterward, the entire Covenant fleet began turning on itself, following Gargantum's example. The, one of the five UNSC ships originally sent to tail Solemn Penance, witnessed the massive encounter as Covenant ships turned upon one another and destroyed themselves in a civil war.

However, Incorruptible did not continue in the orbital battle, as a revered Sangheili fleet commander, Imperial Admiral Xytan 'Jar Wattinree, urged all Sangheili to regroup over the outpost world Joyous Exultation of the Salia system. 'Mantakree obediently left the battle, entering slipspace towards Joyous Exultation. During the pursuit, SPARTAN-II Blue Team dropped in the midst of the chase as the Incorruptible prepared to leave the system, in their captured Covenant destroyer, Bloodied Spirit. Gargantum was incensed that heretic "Demons" had seized a Covenant warship, and diverted one of the three pursuit frigates from the Incorruptible to the Bloodied Spirit. The frigate managed to lower the UNSC-controlled destroyer's shields before the SPARTAN-IIs jumped to slipspace for the Zeta Doradus system. The Sangheili defeated the Jiralhanae fleet and subsequently held High Charity in quarantine. However, this largely failed, due to the Gravemind sending the Indulgence of Conviction, controlled by the Flood, to Earth, in the hopes of infecting it and weakening the Sangheili ships in orbit around the Flood hive. This was successful and the Gravemind was able to leave Installation 05's space and find the Ark.

Aftermath
The battle at Installation 05 was extremely costly with significant political-military consequences for the Covenant and remarkable ramifications for all sentient life in the galaxy. Thousands of Covenant forces were slain in John-117's mission to kill the Prophet of Regret, the race to acquire the activation index from the Control Room, and the massive ground and orbital battles that took place on Installation 05, High Charity, and between the Covenant fleets orbiting over Substance because of the Great Schism.

UNSC losses were remarkably lower because of the small number of forces they brought into the theater of operations, almost solely the crew and soldiers of. Hundreds of Marines and Orbital Drop Shock Troopers, however, were lost in UNSC ground operations: the assassination of Regret and the storming of the Quarantine Zone. A large number were also infected by the Flood and made continual appearances as combat forms in the Sentinel wall, Quarantine Zone, and Flood-infested High Charity. The crewmen of the In Amber Clad were presumably killed and reanimated by the Flood as well. However, the UNSC suffered the least amongst the four warring factions in the Battle of Installation 05. In many ways, Installation 05 was the true turning point in the Human-Covenant War. In the long term, the political chaos wrought throughout the battle would shatter the Covenant into warring factions. The Sangheili eventually allied themselves with their human enemies, bolstering their fleets and taking their military expertise away from the Covenant. The immediate loss of High Charity and the majority of its enormous defense fleet drastically reduced the threat of the Covenant to human space. While still dangerous, the Covenant forces loyal to the Prophets ultimately proved incapable of defending themselves over the last few weeks of the war.

Sentinel defenses were completely trampled over, particularly in the Quarantine Zone, where within hours, the Flood had managed to infiltrate the well-defended Sentinel wall and seize control of large tracts of the Quarantine Zone, even grounding an airborne Sentinel manufacturing facility. The Flood also permeated the Library and the surrounding grounds, eliminating almost all Sentinels from the skies, leaving only scattered Enforcers to do battle with them. The Flood also controlled UNSC and Covenant vehicles alike, reinforcing their considerable ranks with M808B Scorpion tanks, M12 Warthog LRVs, Type-26 Wraith tanks, and Type-32 Ghost assault vehicles. Flood losses were initially high because of the Arbiter's actions in the Quarantine Zone and John-117's on High Charity. However, it was inconsequential: the Flood scored a notable victory on High Charity, capturing the Covenant's mobile home planetoid and transforming the structure into a Flood hive.

Fragmentation of the Covenant
The Covenant was fractured, with the Sangheili rallying those loyal to them against the San'Shyuum and Jiralhanae, who controlled the military of the Prophet-led Covenant against the Sangheili and their allies. Many San'Shyuum were killed in the battle, either during the Flood's infestation of High Charity, or on Installation 05 as many Ministers and Prophets travelled to the ring to examine it for themselves, which effectively led to the near extinction of the San'Shyuum. To make matters worse for the species, those who did not die during the Flood invasion on High Charity were reluctantly forced to stay on the Covenant capital by Rtas 'Vadum and the Fleet of Retribution's quarantine, duo to the danger the Flood posed in case they infected a San'Shyuum-led ship and spread through the galaxy. However, there were San'Shyuum who managed to escape with their shops before 'Vadum discovered the Flood's presence on the city. The Prophets' betrayal of the Sangheili led to the divide of the Covenant species. Many Mgalekgolo allied themselves with the Sangheili, the Unggoy and Huragok followed their commanders, most Yanme'e joined the Jiralhanae and the Kig-Yar aligned themselves with whoever would lead them to profit.

The Covenant ruling system was destabilized, with the death of the Prophet of Regret on Installation 05 at the hands of John-117 and the death of the Prophet of Mercy on High Charity due to Flood infestation. The Prophet of Truth held dictatorial power, with several subservient Minor Prophets, completely re-shifting the political dynamics of the Covenant. The Jiralhanae held reign over the majority of the Covenant military, bringing their innate tenaciousness and ferocity to the front lines quite unlike the Sangheili. The Jiralhanae also assumed more lower-level Covenant military authority, now replacing the Sangheili as the leaders of field squads and teams. The Jiralhanae also introduced a unique set of bloodthirsty weaponry into the Covenant's field arsenals. The Covenant fleet was believed to lose quite a bit of its technical proficiency without the innate technical knowledge of the Sangheili.

Return to Earth
"Terrence Hood"

In the end, the fates of the Covenant fleets over High Charity is unknown, although at least one Covenant vessel, the Incorruptible, escaped. 'Matrankee was commended for his actions against the Flood on Installation 05, and was promoted to Fleet Master. The Flood continued to attempt to escape High Charity in Covenant starships, and a fleet led by Rtas 'Vadum on the Shadow of Intent held the line against the Flood. However, the Flood managed to infest at least one Sangheili-controlled ship, the Indulgence of Conviction, a, and made a slipspace jump to Earth to attempt to infest the human homeworld. The Sangheili fleet in orbit over High Charity followed the Flood-controlled cruiser, and when the Flood ship crash-landed on Earth, Rtas 'Vadum and his forces aided the UNSC Home Fleet in destroying the Flood vessel and terminating the Flood spread across the planet. However, prior to this, High Charity had already left its orbit around Installation 05, and according to a scrambled distress signal from Cortana, was already on its way to Earth to enter the Portal. It was indicated though that all of the other Flood-controlled ships were destroyed though: upon landing on Earth an Sangheili informed the Arbiter that the Sangheili's fleet had taken care of all of the Flood-controlled ships, except for the one which had managed to break through and jump to Earth. It can be inferred that the Flood-controlled ships were ultimately all destroyed except the one intercepted on Earth and High Charity which was later destroyed by the Master Chief in the Battle of Installation 00. Cortana was left to the clutches of the Gravemind. It was later shown that she answered a few questions to buy herself some time and used the opportunity to help find a way to destroy the Flood. She would later be rescued by the Master Chief who would then destroy High Charity during the Raid on High Charity.

John-117 was aboard Truth's Forerunner Dreadnought, which managed to reach Earth unharmed and landed in Africa, near the Portal to the Ark, about two weeks after its departure from High Charity. eventually withdrew to rendezvous with Admiral Patterson's battlegroup outside of the Zeta Doradus system, and the UNSC In Amber Clad remained crashed into one of the towers of High Charity.

Timeline
October 20, 2552
 * The Battle of Earth begins between the UNSC Defense Force and the Covenant's Fleet of Sacred Consecration.
 * UNSC forces heavily outnumber Covenant forces and the Prophet of Regret orders a retreat.
 * With Regret aboard, the Solemn Penance makes an emergency slipspace jump over New Mombasa, followed by, Coral Sea, Dusk, Paris, and Redoubtable.

November 2, 2552
 * Solemn Penance and In Amber Clad exit slipspace in the Coelest system over Substance and near Installation 05.
 * The Battle of Installation 05 begins.
 * Solemn Penance deploys ground forces to the surface of the installation and Regret occupies a Forerunner temple.
 * Regret sends out a distress signal and apology to the rest of the High Council, which the Prophets of Truth and Mercy reluctantly accept.
 * John-117 is deployed to the installation's surface, along with several Orbital Drop Shock Troopers. The UNSC forces fight their way to Regret's position.
 * High Charity, its defense fleet, and the Second Fleet of Homogeneous Clarity arrive in the system.
 * Rtas 'Vadumee sends Type-52 Phantoms to rescue Regret, but Truth belays the order.
 * John assassinates the Prophet of Regret inside the temple and retreats at Solemn Penance attempts to kill him. The Spartan is captured by the Gravemind.
 * The Sangheili's "failure" to protect Regret leads to the Changing of the Guard, as Jiralhanae occupy Sangheili positions.

November 3, 2552
 * Arbiter Thel 'Vadamee and Tartarus are sent to retrieve Installation 05's activation index. The Arbiter successfully takes the index, but Tartarus tries to kill him and takes the index from him, having been secretly ordered to do so by the Prophet of Truth.
 * Most of the Sangheili Councilors are taken to the surface of Installation 05 where they are murdered by the Jiralhanae.
 * The Prophet of Truth transfers command of the Covenant military to the Jiralhanae, while Tartarus declares war on the Sangheili, and the Fall of High Charity begins. Fighting between Sangheili and Jiralhanae forces breaks out all over High Charity. As word spreads, fighting takes place throughout the fleet, as Sangheili and Jiralhanae controlled ships attack one another.
 * The Flood invade High Charity during the battle, entering the city's dome via precision slipspace jump aboard In Amber Clad and its embarked Pelicans. The Prophet of Mercy is attacked by an infection form and abandoned by the Prophet of Truth, who now reigns as the Covenant's sole leader.
 * Tartarus attempts to activate Installation 05 by forcing Commander Miranda Keyes to insert the Index into the Control Room's Core.
 * Thel 'Vadamee, with the aid of Sergeant Johnson and Rtas 'Vadumee, kills Tartarus.
 * Commander Keyes aborts the activation of Installation 05, placing the entire Halo Array on standby status. 343 Guilty Spark reveals the existence of the Ark.
 * The Flood takes control of High Charity and many of its warships. Jiralhanae and Sangheili fleets remaining around the city-station continue to destroy each other.
 * The Prophet of Truth departs High Charity for Earth aboard the Forerunner Dreadnought, to join the Battle of Earth, with John-117 aboard.
 * The prowler Dusk witnesses the battle between Sangheili and Jiralhanae held ships above Delta Halo, both fighting each other pausing only to escalate an immediate outbreak of the Flood from the ringworld. Dusk subsequently flees the battle and links up with Patterson's battle group at Earth.
 * Sangheili Major Voro 'Mantakree kills his shipmaster, Tano 'Inanraree, while he is attempting to allow the Flood] to enter the ship. He then assumes command of the ship, Incorruptible, and becomes the de facto leader of the Second Fleet of Homogeneous Clarity. He leads his new forces to Joyous Exultation, pursued by the Jiralhanae Gargantum and his ships.

November 4, 2552
 * Thel 'Vadam's forces glass Installation 05's surface to neutralize the Flood.
 * The Battle of Installation 05 ends.

Personnel

 * Commander Miranda Keyes
 * Commander Richard Lash
 * Lieutenant Commander Julian Waters
 * Lieutenant Commander Xaing Cho
 * Lieutenant Bethany Durruno
 * Lieutenant Joe Yang
 * Master Chief Petty Officer John-117
 * Sergeant Major Avery Johnson
 * Gunnery Sergeant Marcus Stacker
 * Staff Sergeant Banks
 * Corporal Perez
 * Private First Class Chips Dubbo
 * Private McKenzie
 * Cortana

Forerunner constructs

 * 343 Guilty Spark

Flood

 * Gravemind
 * 2401 Penitent Tangent

Personnel

 * Arbiter Thel 'Vadamee
 * Special Operations Commander Rtas 'Vadumee
 * Councilor Duru 'Scoahamee
 * Councilor K'hurk 'Bornisamee
 * Councilor Torg 'Gransamee
 * Shipmaster Tano 'Inanraree
 * Shipmaster D'ero 'S'budee
 * Commander G'torik 'Klemmee
 * Major Voro 'Mantakree
 * Zo Resken, the Prophet of Clarity
 * Tilik 'Bornisamee
 * Uruo 'Losonaee
 * Zasses 'Jeqkogoee
 * Y'gar 'Pewtrunoee
 * Paruto Xida Konna
 * Waruna Xida Yotno
 * Crun 'Brinsmee
 * Tul 'Imjanamee
 * Sluggish Drifter

Ships

 * Eternal Reward
 * Incorruptible
 * Indulgence of Conviction
 * Journey's Sustenance
 * Lawgiver
 * Rapturous Arc
 * Shadow of Intent

Personnel

 * High Prophet of Truth
 * High Prophet of Mercy
 * High Prophet of Regret
 * Prophet of Exquisite Devotion
 * Minister of Preparation
 * Tem'Bhetek
 * Chieftain Tartarus
 * Shipmaster Gargantum
 * Captain Melchus

Ships

 * Revenant
 * Shadow of Intent (before capture)
 * Solemn Penance
 * Spear of Light
 * Tenebrous
 * Twilight Compunction

List of appearances

 * Halo 2
 * Halo: Ghosts of Onyx
 * Halo 3
 * Halo: Evolutions - Essential Tales of the Halo Universe
 * Wages of Sin
 * Halo: Broken Circle
 * Halo 2: Anniversary
 * Terminals
 * Halo: Hunters in the Dark
 * Halo: Last Light
 * Halo: Shadow of Intent