Battle of Installation 05

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"Even as the humans' annihilation filled us with satifaction, the loss of one of the Sacred Rings wracked our hearts with grief."

- Prophet of Mercy

"Putting aside our sorrow, we renewed our faith in the prophecy that other rings would be found. And see how our faith has been rewarded."

- Prophet of Truth

The Battle of Installation 05, also known as the Battle of Delta Halo (or the Battle for the Second Ring of the Gods among the Covenant, ), was a major engagement between the United Nations Space Command, Covenant, Sentinels, and the Flood on the Forerunner ringworld Installation 05, otherwise known as "Delta Halo".

Introduction
At the beginning of the Battle of Earth, the Prophet of Regret led a small fleet of two Assault Carriers and thirteen s on an expeditionary raid that stumbled upon Earth, the strongest remaining UNSC planet, as well as the homeworld of humanity. After substantial losses, Regret fled in an Assault Carrier over New Mombasa, opening a Slipspace rift and destroying the city in a devastating Slipspace cataclysm as it initiated an emergency jump, inside the Earth's atmosphere, to Installation 05. How the Covenant obtained the coordinates to Installation 05 is unknown.

However, upon Fleet Admiral Hood's order, five United Nations Space Command warships near New Mombasa were close enough to catch onto the Assault Carrier's rift before it terminated: three UNSC Frigates, the, , and the , one UNSC corvette, the , and one UNSC prowler, the , were able to enter the Slipspace field, trailing the Assault Carrier.

Their shadowing, however, was not exactingly precise. Only the frigate In Amber Clad successfully trailed the Assault Carrier to Installation 05. The prowler Dusk arrived days later near the Covenant homeworld ship High Charity, and the Coral Sea, Paris, and Redoubtable were nowhere near the engagement, most likely due to the imprecise physics of Slipspace and the UNSC's rather limited technology in that field.

UNSC Offensive
Regret's assault carrier hovered over the installation, deploying Wraiths, Ghosts, Banshees, and also companies of Elites, Jackals, Drones, and Grunts by means of Phantom dropships. The Covenant ground forces fortified themselves in a series of Forerunner ruins and temple structures, even establishing Shielded Plasma Cannons for further defense.

Meanwhile, the In Amber Clad trailed behind, and after the Assault Carrier moved off, Commander Miranda Keyes, captain of the 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 J. Johnson to bring in two flights of Pelicans and further expand the UNSC presence. The frigate made a quick pass-over of a segment of the ringworld, deploying a dozen Human Entry Vehicles (HEV). Six survived the atmosphere of the ring, and only four personnel eventually survived the impact - SPARTAN-117 and three "Helljumpers". However, before they could land in the small ruins, they were detected by the Covenant, and SPARTAN-117 led the commandos in eliminating Covenant plasma turrets and holding their position against waves of Covenant troops until a Pelican could drop off an M12 Warthog LRV and a pair of Marines.

While the immediate objective for SPARTAN-117 and his Marines was to push through the Covenant-held Forerunner ruins and assassinate the Prophet of Regret, the overall UNSC objective for Installation 05 was to ensure that the Covenant would not activate the ring and extinguish all sentient life in the galaxy. To accomplish this objective, the UNSC ground forces moved to capture the Library and retrieve the installation's Index, thereby preventing the Covenant from using it to fire the ring.

After SPARTAN-117 and his men pushed through two Forerunner ruins, another Pelican air-dropped Resupply Canisters and a small number of Marines, refueling the UNSC offensive as they advanced through a ravine defended by Jackal Snipers and Drones. They proceeded to another temple, this one with a hologram of the Prophet of Regret, who was sermonizing in a main Forerunner temple to prepare for the activation of the ring and the sublimation event of the "Great Journey". After learning all of the information the Prophet could provide, his elimination became the primary objective for SPARTAN-117, as his death would destabilize the Covenant politically and religiously. After Cortana deciphered the hologram, SPARTAN-117 and a pair of Marines battled through a pair of Covenant-held temples before reaching an open platform. At this time, the Covenant became aware of UNSC activity, and increased their defenses. Commander Keyes responded by sending several Pelicans towards John-117, which air-dropped more Resupply Canisters on the platform.

Proceeding from the platform to a gondola, SPARTAN-117 and his remaining Marines assaulted a heavily-defended Forerunner underwater temple, which was guarded by Hunters, Stealth Elites, Honor Guard Elites, Stealth Grunts, and other Covenant forces. After emerging from the submerged temple, they arrived at a Forerunner ruin, where Drones, Elites, and Grunts attempted to halt the UNSC advance, and Phantoms arrived with additional Covenant reinforcements.

Assassination
However, the Covenant were ultimately unsuccessful. The UNSC, after clearing out the last ruins, were able to secure a landing zone for a Pelican to air-drop Resupply Canisters and a team of Marines, who aided SPARTAN-117 in the final push towards the main temple. The UNSC forces commandeered an additional gondola they found near the tower. Despite heavy resistance from Banshees and Rangers, they were able to gain access to the temple. After destroying several defense turrets, the small strike force entered the Temple as the Prophet of Regret was finishing his sermon.

After docking, High Charity reverted from Slipspace over Installation 05, with hundreds of warships, including those of 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 SPARTAN-117 and defend the Prophet leader. However, the Prophet of Truth diverted the Phantoms deliberately, allowing the SPARTAN-II to kill Regret as part of his socio-political plans for the Covenant.

"How dare you interrupt my sermon? Guards, remove him! Your very existence offends me, Demon!"

- Prophet of Regret

A large contingent of Honor Guards and Grunts defended the Prophet. These forces were quickly bested however, and SPARTAN-117 attacked his target directly. Eschewing firearms which were useless against Regret's force shield, Master Chief boarded the High Prophet's gravity throne and beat him to death with MJOLNIR enhanced blows. Shortly thereafter, a Covenant Assault Carrier repositioned over the main temple, destroying it with a gravity beam and killing all remaining Covenant and UNSC forces on site. SPARTAN-117 jumped (or fell) into the lake with seconds to spare and was grasped by the tentacles of the Gravemind, a Flood overlord creature, and taken prisoner.

Introduction
"You will journey to the surface of the ring, and retrieve this Sacred Icon. With it, we shall fulfill our promise, and begin the Great Journey."

- Prophet of Truth to the Thel 'Vadam

After the Prophet of Regret had been murdered, an event that would soon help to spark the Covenant Civil War, the UNSC and the Covenant both raced to reach the Library and seize the 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 Halos.

Changing of the Guard
"Recommissioning the guard was a radical step, but recent events have made it abundantly clear that the Elites can no longer guarantee our safety."

- Prophet of Truth to Rtas 'Vadumee

After the assassination of Regret at the hands of the Demon, Rtas 'Vadumee was furious at the Prophet of Truth for withdrawing his men at the last minute. However, Truth deliberately shifted blame to the Elites and stated that the Sangheili's greatest warriors had ultimately failed in their charge to protect the High Prophets. The Honor Guards of the Covenant were decommissioned, and the Brutes took over as the guardians of the Prophet hierarchy, a political move that infuriated the Elites and drove an even deeper rift between the Brutes and the Elites, who were already mortal enemies.

Containment Shield
"Once the shield is down, we'll head straight to the Library. I do not wish to keep the Hierarchs waiting."

- Tartarus to the Arbiter

However, 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 the Sentinel Wall, a large underground Forerunner complex heavily defended by Sentinels, Sentinel Majors, and even Enforcers. Numbers of Brutes, Jackals, and Grunts had already attempted to penetrate the Sentinel Wall, with pockets scattered all over the facility, all being overwhelmed by Sentinel defenders. However, the Arbiter was air-dropped by 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.

After battling through the forward section of the Sentinel Wall and moving even deeper through the facility, the Arbiter was able to destroy an Enforcer, and disengage the plug locks of the generator, and then physically disengage the generator out of its "cradle", powering off the Containment Shield. While the shield had been disengaged, the path to the Library was far from clear. There was a rampant Flood infestation: the second half of the Sentinel Wall was heavily saturated with Flood, and there were icy canyons heavily entrenched by Flood battling against outnumbered Sentinel defenders that lay between the perimeter of the Containment Shield and the Library, which was accessible only by an underground gondola.

"Blasted machines! Make your own a way through the wall, Arbiter!"

- Tartarus to the Arbiter

Tartarus attempted to pick up the Arbiter and move directly to the Library, but his Phantom was engaged by an Enforcer, forcing the Arbiter to battle through 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 Elites to clear out the lower levels of the complex, but these too were killed. Finally, the Arbiter jumped down a series of plummeting vertical tunnels, exiting from the Sentinel Wall and entering the battle-torn icy plains of the Quarantine Zone.

Battle of the Quarantine Zone


"The Flood are upon us!"

- Special Operations Elite

"We must hold this camp until reinforcements arrive."

- Special Operations Commander Rtas 'Vadumee

The Quarantine Zone was supposed to be a location where during times of war, the Sentinel custodians of the installation could herd the Flood, and prevent them from entering the Library. Two Sentinel Constructor Factory 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 factories, sending it plummeting down to the ringworld.

The Covenant shortly established a "camp", air-dropping seven drop pods that contained Rtas 'Vadumee and six Special Operations Elites, along with several plasma turrets and a deployable gravity lift tower.

"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. Go, Arbiter, I'll follow when our reinforcements arrive."

- Rtas 'Vadumee

The Arbiter met with three of the Elites just outside of the Sentinel Wall, and together, they defended a makeshift Firebase from the Flood before pushing inwards, where the Special Operations Commander had landed and established a small outpost, complete with turrets and the gravity lift tower, where 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 Spectre and a pair of 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 Elites and the Arbiter, the UNSC were swifter to advance through the Quarantine Zone - the 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-commandeered Ghosts, Warthogs, Wraiths, and Scorpions, while Enforcers continuously rained heavy fire.

The small Covenant task force was forced to debark from its vehicles as they navigated the wreckage of one of the Sentinel Constructor Factories, although just beyond the wreckage they were met by another Covenant Phantom, this one dropping off a Spectre manned by Rtas 'Vadumee himself and another Special Operations Elite. As they progressed through the last series of snowy plains and neared the Library, they were met with increasingly heavy resistance. 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 from gaining entrance to the Library and retrieving the Index - the use of which would lead to the extermination of all sentient life, as well as the Flood.

Library
"More humans...they must be after the icon."

- Rtas 'Vadumee to the Arbiter

However, a small UNSC Marine force led by Miranda Keyes and Avery J. Johnson was able to slip through, and, in the end, the Arbiter, Rtas 'Vadumee, and half a dozen Special Operations Elites were able to slip into the periphery of the Library. There were a pair of gondolas that, when activated, automatically 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 Elite, holding them at the entrance to the gondolas to defend the rest from the Flood as the Arbiter took four Special Operations Elites on the second gondola, trailing behind the UNSC-held one.

"Humans! I'll get them."

- Tartarus

"That fool! He'll alert them to our presence!"

- First Special Operations Elite

"Look on the bright side, maybe if we're lucky, they'll shoot him down!"

- Second Special Operations Elite

The gondola ride, however, was harrowing. The Flood attacked from all sides, assailing both the UNSC troops as well as the Arbiter and his quartet of Special Operations Elites. 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.

"Behold, the library of our lords!"

- Special Operations Elite "The humans are already inside, Arbiter! After them! I'll watch the perimeter. Hurry, Arbiter! Get the icon!"

- Tartarus

"We shall protect this vessel. It may be our only means of escape."

- Special Operations Elite

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 (four Marines (including Perez and McKenzie) led by Miranda Keyes and Avery Johnson, entered. Although many Combat Forms had been exhausted in the Flood's last-ditch attempt to stave off the gondolas, there were a large number of Infection Forms prowling the Library which killed off the four UNSC Marines as Keyes and Johnson advanced towards the core of the Library. The Arbiter shadowed the surviving humans, who remained unaware of his presence.

"McKenzie, Perez, how's our exit? You hear me, Marines?...we got trouble."

- Sergeant Major Avery J. Johnson

While the UNSC forces deployed from In Amber Clad had suffered near total loss, Commander Keyes was able to secure the Index, but only for a moment. Sensing movement, the two cautiously began to edge away from the core, with Johnson readying his BR55 Battle Rifle and Keyes hefting her pair of M7/Caseless Sub Machine Guns. However, the Arbiter quickly rendered Sergeant Johnson unconscious, and proceeded to disarm the Commander just as easily. Before she could react, Tartarus entered with four of his Brute Captains. Tartarus used his Gravity Hammer, the Fist of Rukt, to stun Keyes and levitated her towards him. With the leader of the humans captured and the Index secured, the Covenant seemed poised to triumph.

"The Icon...is my responsibility."

- Arbiter

"Was your responsibility. Now it is mine. A bloody fate awaits you and the rest of your incompetent race. And I, Tartarus, Chieftain of the Brutes, will send you to it!"

- Tartarus

"When the Prophets learn of this, they will take your head!"

- Arbiter

"When they learn? Fool, they ordered me to do it."

- Tartarus

With the Library cleared of hostiles, the Arbiter demanded to have the Index, as he was personally ordered by the Prophet of Truth to secure it for the Covenant. However, unbeknownst to him, he had been betrayed by the Prophets, as had the entire Elite race. The Prophets had named the Brutes their new champions, a race both heavily militarized, and unquestionably loyal to them and their Great Journey.

Tartarus refused to give the Sacred Icon to the Arbiter, and instead, his Brute Captains leveled their Brute Shots at the Arbiter as Tartarus revealed the betrayal. Johntan swung his Gravity Hammer, sending a shock that knocked the Arbiter into the bottomless chasm above which the Index was once situated.

This event turned out to be a mixed blessing for UNSC forces at the Library. While most of the deployed Marines had been slaughtered by the Flood and Covenant, the betrayal of the Elites would be the spark that ignited the Covenant Civil War. Ironically, the Prophet's lust for the sacred Rings would prove to be their undoing. Seizing control of In Amber Clad, the Flood would soon pour into High Charity. The center of all Covenant military and political power was to become fodder for an infestation on a galactic scale.

"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

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.

Introduction
However, the Covenant would not activate the Halos unimpeded. Both the Flood and the tattered remains of the UNSC moved to attack High Charity directly. After the fragmentation of the Covenant into the Covenant Loyalists and the Covenant Separatists, the Separatist faction began engaging Brute and Flood forces, with Halo's overwhelmed Sentinel drones engaging all targets of opportunity. What had begun as a simple raid on Earth had escalated out of control into an unprecedented five-sided battle.

"There is still time to stop the key from turning, but first it must be found. You will search one likely spot, and you will search another. Fate had us meet as foes, but this ring will make us brothers."

- Gravemind to John-117 and The Arbiter

Meanwhile, SPARTAN-117 and the Arbiter were both ensnared by plant-like tentacles and dragged into the lower reaches of Installation 05. It was here they met face-to-face with the Flood central sentient intelligence known as the "Gravemind", along with the Prophet of Regret and 2401 Penitent Tangent, the monitor of Installation 05. The Gravemind explained to the Arbiter the true purpose of the Halo installations. Seeking his continued survival, the Gravemind 'recruited' SPARTAN-117 and the Arbiter to face a common enemy. The Flood would manipulate Halo's teleportation grid, sending SPARTAN-117 to High Charity, and sending the Arbiter to the cliffs just beyond the Control Room to search for the Index.

Battle of High Charity


"The demon has entered the council chamber? Protect the Hierarchs! Seal the exits!"

- Tartarus

SPARTAN-117 was teleported by the Gravemind directly into the High Council Chamber of High Charity, where the Prophets of Truth and Mercy reassured the Covenant that the Sacred Icon was secure. Before SPARTAN-117 could kill both Prophets, the doors were locked and waves of Honor Guard Brutes, Minor Brutes, and Grunts entered in an attempt to kill the Demon. Cortana managed to unlock the portals, and SPARTAN-117 began his pursuit of Truth. Shortly thereafter, Cortana picked up the IFF transponder signals of surviving UNSC Marines - prisoners of the Covenant being kept in two brigs in a multitiered detention block.

"Wait a minute! I'm reading Marine IFF transponders. The signals are originating somewhere below your position!"

- Cortana to John-117

Cortana managed to reverse a central gravity lift, allowing SPARTAN-117 to enter the detention block. However, Tartarus had anticipated this, increasing security around the brigs, and a massive firefight ensued as SPARTAN-117 released the Marines. Hopelessly outnumbered but resolute, the small group of soldiers continued their hunt for the Covenant Prophets.

"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

What had begun as a political, "changing of hats" within the Covenant quickly escalated into all out war. The Covenant splintered in the minutes after SPARTAN-117 emancipated the captive Marines. The Prophet of Truth, in three sentences over the loudspeakers of High Charity, put his plan to replace the Elites into action. Truth ordered the entire Covenant to follow the Brutes as their new, defacto military commanders. The Elites, seething in hatred against the Brutes who had assassinated their entire ruling Council, had finally had enough. The Elites burst into all-out warfare on both on High Charity and across the rest of the Covenant empire. While the Grunts and Hunters followed the Elites, the Jackals and the Drones supported the Prophet-blessed Brutes. Warship crewmen began to open fire upon each other, with entire Covenant fleets following suit.

Truth's transmissions, however, allowed Cortana to triangulate his position and direct SPARTAN-117 and his Marines in their hunt for the Prophet. The Covenant attempted to stop Cortana, but were unable to prevent her from accessing their systems. As SPARTAN-117 and the Marines reached the Hanging Gardens A, the first scene of Covenant fratricide was seen, as Honor Guard Elites, Minor Elites, Hunters, and Grunts fought against Brutes and Jackal Snipers. SPARTAN-117 and his men advanced to the Mid-Tower, where Rangers and Special Operations Elites entered the fray, and the Brutes unleashed their Drones into the combat.

Even as the imprisoned Marines were freed, the crew of the In Amber Clad were in peril. Unsurprisingly, the Gravemind double-crossed the UNSC, sending SPARTAN-117 hunting for the Index in the bowels of High Charity while teleporting Flood forms into the UNSC frigate, overpowering the crew. The Gravemind then teleported the In Amber Clad from the atmosphere of Installation 05, sending it into a Slipspace reversion over High Charity, where it plummeted uncontrollably, crashing into the Far Tower.

"Once the towers are clear, we'll drive them from the lower districts!"

- Tartarus

However, by the time that the small UNSC squad entered Hanging Gardens B, Covenant Separatist resistance on High Charity had broken. In the second Hanging Gardens, the Covenant Separatists fell back, leaving behind large numbers of Stationary Shield Generators, abandoning numbers of Grunts to berserk Brutes as the Elites fell back to the Far Tower and the Mausoleum of the Arbiter, drawing a last line of defense there. In the forward sections of the Far Tower, the Separatists held a choke-point bridge with a pair of plasma turrets, Special Operations Elites, and a pair of Hunter warriors. In the Mausoleum of the Arbiter, Specialist Ultra Elites and Hunters fought against waves of attacking Brutes. Despite their efforts, the Prophets of Truth and Mercy, Tartarus, and a handful of Brute Captains were able to tunnel through the last Separatist defenses to the far docking bays of the Far Tower. SPARTAN-117 pursued Tartarus, fighting through the Far Tower and the Mausoleum of the Arbiter to reach the Phantom launch pads.

"Your pal. Where's he going?"

- John-117

"Earth...to finish what we started. And this time, none of you... will be left behind..."

- Prophet of Mercy's last words

However, SPARTAN-117 arrived too late to prevent the Prophet's escape from the interior of the city. The Prophet of Truth ordered Tartarus to use the Sacred Icon in the Control Room of Installation 05 and activate the Halo array, completing the Great Journey. Tartarus took a detachment of Brute 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 Ship - the central energy source of High Charity, and also a fully functional starship that the two remaining High Prophets were going to use to reach Earth, and "finish what The Prophets started".

Simultaneously, the Flood had escaped the crashed hulk of the In Amber Clad. They emerged from the rents in its hull armor, commandeered its Pelican dropships, and sent them over the surface of High Charity. Each ship acted as a vector for the Flood contagion, unleashing Combat Forms, and Infection Forms on soldiers and civilians alike. Their advance across the city soon became unstoppable. The Prophet of Mercy was attacked by one such Infection Form, and was subsequently killed and reanimated as a Flood form. In the span of a few hours, the Covenant had lost two of the three members of its triumvirate. However, Tartarus and Truth were able to depart the dying station before SPARTAN-117 could arrive.

"That structure at the center of the city! It's a Forerunner Ship...and Truth is heading straight for it! If he leads the Covenant fleet to Earth, they won't stand a chance. You have to stop him!"

- Cortana to John-117

Temporailly thwarted, SPARTAN-117 continued his pursuit through the vast capital in an effort to board Truth's Forerunner Dreadnought directly. Allowing the Prophet to escape, given their declared purpose was to complete the destruction of humanity's homeworld, was unacceptable. By that time, Covenant Separatist resistance had completely shattered on High Charity. There were few Elites and Hunters remaining, with the Grunts fairing even worse. The Loyalists, however, retained a large number of Brutes, Jackals, and Drones. Despite the lack of a Separatist ground force, they were still very much present in space, where the Covenant fleets over High Charity had splintered in allegiances, with Elite and Brute 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 SPARTAN-117's position. However, High Charity had become horribly twisted within minutes: an insidious Flood presence spread surprisingly quickly through the planetoid, disrupting power, creating a dark, gloomy atmosphere, spreading Flood spores into the air, covering large parts of High Charity in Flood biomass, and sending Flood forms all across the city-space, where the Flood fought to take High Charity from the remaining Covenant Loyalist forces.

SPARTAN-117 entered the Mausoleum Tower from the Phantom landing pads, battling through numerous Flood combat forms and surviving Covenant forces. The Flood wasted little time in converting the environment of the city to suit their needs. Meanwhile, the Prophet of Truth sent propaganda broadcasts throughout the city. Shortly thereafter, the Gravemind manipulated the station's loudspeakers, proclaiming that the Flood would infest High Charity and send the Covenant to their graves. SPARTAN-117 continued through the massive interior of the Mausoleum Tower, where he took a Gravity Lift to access the Inner Sanctum: the personal quarters of the Hierarchs.

There, a line of Honor Guard Brutes and Jackals had made a final stand against the Flood. Yet ultimately, their efforts proved futile against the combined assault of SPARTAN-117 and the Flood. Entering the energy conduit leading to the Forerunner Ship, SPARTAN-117 was able to successfully board the Dreadnought before it lifted off. With Covenant forces in orbit routed, the battle's final stages moved to the surface of Halo. Tartarus still held the Index, and was determined to activate Installation 05. Cortana announced that she would detonate the fusion reactors of the In Amber Clad if necessary to stop Halo's firing, just like she had done to the UNSC Pillar of Autumn at Installation 04. The massive explosion would destabilize the ring and prevent the activation of the remaining Halo arrays. However, Cortana, who had remained behind in High Charity's computer systems, was captured by the Gravemind before she could put her plan into motion. Subjected to mental torture, her eventual fate, and that of the Gravemind, would later be decided at the Battle of Installation 00 a few short weeks later.

Uprising
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 Brutes were now the ruling caste of the Covenant, Tartarus ordered the execution of the Elite 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, a small number were taken prisoner by the Brutes. The rest of the Covenant garrison, however, was not so fortunate. A hovering close to the Control Room was taken by the Brutes from the Elites, and a large number of Minor Elites and Grunts stationed in the cliffs above the Control Room were killed. However, there were still a number of Grunts that managed to resist, although they were terrified by the murders of their Elite superiors and Grunt comrades.

Meanwhile, Tartarus took his two Phantoms from High Charity to the surface of Installation 05, with himself, the Sacred Icon, and Miranda Keyes in one dropship, and Johnson and two other anonymous Marine prisoners in the other. Tartarus debarked from his own Phantom onto the Control Room, with Keyes and the Index in his grip. The other Phantom diverged, however, and by unknown means, the three Marines freed themselves from their Phantom aboard the docking platform. Avery J. Johnson was able to seize control of the docked Scarab while the other Marines fought off a large number of Brute Captains with Plasma Pistols.

However, there was soon a reorganized resistance movement: the Gravemind teleported the Arbiter to a high cliff south of 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 of the Prophets, but only death and destruction on a galactic scale. The Arbiter witnessed the murders of a handful of Elites from afar at the hands of the Brutes, but was able to push forward against a number of patrolling Brutes. Taking command of the scattered surviving soldiers, the Arbiter swore vengeance against the Brutes for the murders of their brothers. The small unit wasted little time, unpinning small groups of scattered loyal Grunts and killing dozens of Brutes, Jackals, and Drones. Taking their enemies off guard, the Arbiter was able to commandeer a number of Ghosts which proved invaluable throughout the Separatist advance.

The Loyalists attempted to set a trap for the advancing Arbiter and his allies, laying a large number of exploding weapons canisters to block a narrow stretch of the canyon. Even this measure was unsuccessful as the Separatists pushed towards a Brute weapons depot. The Separatists charged the depot, which was holed in a large Forerunner facility. The defenses were formitable, including heavily armored Wraith plasma tanks and many veteran soldiers. After securing the first half of the camp, the Arbiter moved into the depot itself, where the Brutes had aggregated a large number of Covenant and UNSC weapons alike, including M19 Rocket Launchers, M90 Assault Shotguns, Fuel Rod Guns, Brute Shots, and a variety of other weapons. Ironically, the supposed holy guardians of the Prophets quickly demonstrated their own heresy in their indifference towards using captured UNSC armaments.

As the Arbiter continued towards the second half of the encampment, the Loyalists became increasingly desperate, sending a group of reinforcements, including Ghost vehicles from another base, the Bastion of the Brutes. This was ultimately unsuccessful, and the Arbiter was able to advance to meet more friendly units, including Rtas 'Vadumee, who learned from the Arbiter of the Councilors' murder. Rtas 'Vadumee indicated 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. Only a Scarab walker held sufficient firepower to breach the inner sanctum. With little time remaining, the Elites moved to capture Bastion of the Brutes in order to secure such a vehicle.

While Rtas 'Vadumee advanced forward in a Wraith tank, the Arbiter and his surviving warriors secured an entrance into the base. The Arbiter quickly turned the tables on the forces within by freeing a number of elite soldiers being held prisoner. They wasted little time in exacting vengeance upon their captors. Rtas 'Vadumee declared he would remain behind to cover the Arbiter's advance, preventing any flanking attack. Accomplishing this objective, he announced that he would retake the captured Separatist battlecruiser responsible for deploying enemy reinforcements.

The Arbiter, followed by his ad-hoc unit of liberated Hunters and Elites, was able to kill the Brute Captains guarding the platform, freeing two UNSC Marines (Marcus Banks and Marcus Stacker) in the process. However, Sergeant Johnson still had command of the Scarab, and aimed its main cannon directly at the Arbiter. In a rare show of inter-species goodwill, Johnson offered the Arbiter a deal. It was in the interest of both the UNSC and the Separatists to prevent Tartarus from using the Index to activate the Halo array. Johnson quickly drafted a plan: He would pilot the walker, while the Arbiter escorted him in a Banshee. Together, they would breach the Control Room and prevent the firing of Installation 05. Though it was a small moment in a vast war, this incident was the first time Sangheili and UNSC personnel officially launched a joint attack on their now common enemy: the Covenant Loyalists.

A formidable defensive line awaited the unlikely allies. No less than five Wraith tanks and two Spectres were stationed to prevent the Scarab's passage, with an additional four plasma turrets mounted on the cliffs. In a drastic miscalculation, not only did the plasma munitions of the Loyalist vehicles do no noticeable damage to the heavily armored Scarab, Sergeant Johnson was able to crush opposing enemy armor outright. The Loyalists, acting out of desperation, sortied an airstrike against the Scarab. It ultimately failed to cause any damage to the walker, and the surviving flyers were quickly shot down by the Arbiter's Banshee.

Control Room
Shortly afterwards, the Scarab arrived before the Control Room and melted through the armored doors with direct cannon fire. The Arbiter then fought his way through large numbers of Brute Captains and Brutes Honor Guards. Despite reinforcements, the highly-ranked Brutes were unable to check his advance, and the Arbiter continued down an arched corridor before confronting Tartarus in the central control room.

Tartarus had been trying to force his prisoner, Miranda Keyes, to place the Sacred Icon into its receptacle on a holographic control panel in the massive central control chamber of the Control Room. Keyes, even under great pain, refused to do so, enraging the brute chieftain. When the Arbiter arrived, he demanded that Tartarus put her down, and attempted to reason with Tartarus, urging him that the Prophets had in fact betrayed them all. 343 Guilty Spark, who himself was a prisoner of Tartarus, confirmed the Arbiter's arguments. Unswayed, Tartarus lost all patience. Clutching the Sacred Icon and forcing Miranda Keyes to put it into its receptacle, he began the activation of Installation 05. Behind their platform, a massive Forerunner multitiered construct began to open up: a three-storied structure, which at its center, boasted a brilliant gravitic column. Halo had begun its firing process.

Miranda jumped out of the way of the imminent firefight as the Arbiter, Sergeant Johnson, and a small cluster of recently arrived Zealots and Councilors charged at Tartarus and his elite guard. Almost immediately, the four captains were slain, and Tartarus was forced back to the recently unveiled three-story structure. 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. While the Zealots and Councilors drew their Energy Swords and charged, Tartarus openly mocked them, allowing them several blows before drawing his massive Gravity Hammer, the Fist of Rukt, and sending them to their deaths with a single blow.

343 Guilty Spark announced that the installation was priming to fire. With time running out, Sergeant Johnson found that he could overload Tartarus' shields for a brief time with three successive bursts from his beam rifle. The Arbiter soon developed a tactic. He would wait for Johnson to lower Tartarus' shields with his beam rifle shots, and then rush in and attack Tartarus while his shields were down. After a long, protracted fight, the Arbiter was able to fire a finishing blow to Tartarus, ending the reign of the chieftain of the Brutes.

Miranda Keyes immediately leapt to action after Tartarus died, snatching the Index triumphantly from the control panel. Despite the fact that Installation 05 was primed to fire, because of Miranda's quick actions, 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 warned that the threat of the Halo arrays was not over: because of the partial activation of Installation 05, the other six remaining installations were set onto standby mode. Each was primed, and ready to fire upon command from a central Forerunner installation: the Ark, one of the portals to which was located near Voi, Africa on the planet Earth.

Orbital Battle
While ground battles raged over the contested lands of High Charity and Installation 05, the Covenant fleets, divided, had not been idle or inoperative. During the hours which the Loyalists and the Separatists warred for the districts of High Charity, the Covenant fleet had splintered within itself, and its warships were destroying each other systematically over the planetoid as Brute-controlled warships raged against Elite-controlled ones. However, after the Prophet of Truth's departure in the Forerunner Ship, the fighting cooled as many ships fell silent, wondering what loyalties to assume in light of Truth's sudden abandonment and Tartarus's death, although a small number of starships continued fighting.

Despite the isolated Separatist 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 Major Domo Elite Voro 'Mantakree assumed command of the Incorruptible, and audaciously sent a fleetwide dispatch to the idling Covenant fleet amassed over High Charity: the Flood were lifting off from Installation 05 in DX-class "Spirit" dropships and Banshees and were attempting to attack and take control of Covenant warships to spread throughout the galaxy. Surprisingly, even divided political opponents 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 Alpha Jiralhanae Gargantum attempted to coordinate a Loyalist uprising against the Elites, and chased with four Covenant Frigates after 'Mantakree. Using deft tactics and maneuvering out the Separatist carrier Lawgiver, the Incorruptible destroyed the Brute-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 UNSC Dusk, one of the five UNSC ships originally sent to tail Regret's Assault Carrier, witnessed the massive encounter as Covenant ships turned upon one another and destroyed themselves in a civil war.

However, the Incorruptible did not continue in the orbital battle, as a revered Elite fleet commander, Imperial Admiral Xytan 'Jar Wattinree, urged all Elites to regroup over the outpost world Joyous Exaltation of the Salia system. 'Mantakree obediently left the battle, entering Slipspace towards Joyous Exaltation. During the pursuit, UNSC SPARTAN-II Blue Team dropped in the midst of the chase as the Incorruptible prepared to leave the system, in their captured Covenant Destroyer, the 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 SPARTANs jumped to Slipspace for the Zeta Doradus System.

It is heavily implied in Halo 3 that the Covenant Separatists defeated the Brute Fleet and subsequently held High Charity in quarantine. However, this largely failed due to the Gravemind sending a single ship, controlled by the Flood, to Earth, in the hopes of infecting it and weakening the Elite 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.

Conclusion
The Battle of Installation 05 was an extremely costly battle with significant political-military consequences for the Covenant and remarkable ramifications for all sentient life in the galaxy. Thousands of Covenant forces were killed during SPARTAN-117's mission to kill the Prophet of Regret, the race to acquire the Index from the Control Room, and the remarkable ground and orbital battles that took place on Installation 05, High Charity, and throughout Covenant fleets. The Covenant was irreversibly fractured, with the Elites rallying the Covenant Separatists against the Prophet-supported Brutes, who controlled the Covenant Loyalists against the Elites and their allies.

The Covenant ruling system was destabilized, with the death of the Prophet of Regret on Installation 05 at the hands of SPARTAN-117 and the death of the Prophet of Mercy on High Charity at the hands of the Flood. The Prophet of Truth held the ultimate power now, with several Minor Prophets, completely re-shifting the political dynamics of the Covenant. The Brutes now held reign over the majority of the Covenant military, bringing their innate tenaciousness and ferocity to the front lines, quite unlike the more methodical Elites. The Brutes also assumed more lower-level Covenant military authority, now replacing the Elites as the leaders of field squads and teams. The Brutes also introduced a unique set of weaponry into the Covenant's field arsenals. The Covenant fleet was believed to have lost the majority of its technical proficiency without the technical knowledge of the Elites and their allies. This was further compounded by the near extinction of the entire San 'Shyuum race, who maintained a near total monopoly of reverse-engineered Forerunner technology.

Sentinel defenses were completely overrun, particularly in the Quarantine Zone. 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 Constructor Factory ship. 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, Wraith tanks, and Ghost vehicles. Flood losses were initially high because of the Arbiter's actions in the Quarantine Zone and SPARTAN-117's actions on High Charity. However, it was inconsequential: the Flood managed to terraform and transform High Charity into another of their "wretched hives", capturing the Covenant's mobile home planetoid.

UNSC losses were remarkably low because of the small number of forces brought into the theater of operations, almost solely the crew and soldiers of the UNSC In Amber Clad. Hundreds of Marines and Orbital Drop Shock Troopers were lost in UNSC ground operations: the assassination of Regret and the storming on the Quarantine Zone, and a large number were infected by the Flood and made continual appearances as combat forms in the Sentinel Wall, Quarantine Zone, and Flood-infested High Charity. The crew members of In Amber Clad were presumably killed and reanimated by the Flood as well. Despite this, the UNSC suffered the least casualties amongst the five warring factions in the Battle of Installation 05.

"John-117? Mind telling me what you're doing on that ship?"

- Fleet Admiral Hood

"Sir. Finishing this fight."

- SPARTAN-117

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 Covenant Separatist 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 Elite-controlled ship, a and made a Slipspace jump to Earth to attempt to infest the human homeworld. The Elite 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 that all of the other Flood controlled ships were destroyed when, upon landing on Earth, an Elite informed the Arbiter that the Elite's fleet had taken care of all of the Flood controlled ships, except for that 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 that jumped to Earth and High Charity which was later destroyed by John-117 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 John-117, 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. The UNSC Dusk eventually withdrew to rendezvous with Battlegroup Stalingrad shortly outside of the Onyx System, and the UNSC In Amber Clad remained crashed into one of the towers of High Charity.

Militarily, SPARTAN-117 was once again able to lead a successful guerrilla battle against both factions of the Covenant on the surface of Delta Halo, and later within High Charity itself. The Elite and Brute defense fleets devastated each other, sparking multiple battles all across Covenant space. Although Loyalist forces remained numerically superior for the remainder of the war, they were now forced to split their attention between human and sangheili targets.

Politically, the union which had once united seven races had been shattered along sectarian lines. The Elite led Separatists eventually allied themselves with the UNSC, bolstering the allied fleets as well as contributing their greatest remaining warriors. Moreover, the infection of High Charity was a catastrophic loss for the entire San 'Shyuum people. It is estimated that less than a thousand of their race remained alive by the conclusion of the war, and only those individuals stationed away from the battle itself. This in turn left the other races of the Covenant in a state of decay, and possible collapse, as their combined technology was imitative rather than innovated.

In many ways, the Battle of Installation 05 was the true turning point in the Human-Covenant war. The UNSC was able to successfully assassinate a High Prophet and prevent the Halo arrays from firing, at the cost of a single Frigate and most of its crew. The Prophets had considered replacing the Elites with the more easily manipulated Brutes for some time, yet the death of Regret in many ways forced Truth's hand at a critical moment during the Covenant's campaign against humanity. While the Covenant maintained sufficient military forces to defeat the UNSC and their Separatist allies, it had lost the three pillars of its own civilization: the San 'Shyuum's secrets of Forerunner technology, the Elites' military leadership, and its capital city of High Charity. Losses were high on both sides of the conflict, yet for the Covenant, it was strategically a deathblow the Empire would never recover from.