Battle of Requiem

"Non-believers walk the sacred ground. Purge the heretics, so they not foul the air of Paradise. The time has come to enter the Great Light. The Promethean awakening is nigh, our reward is at hand."

- A transmission from Jul's Covenant (translated by Cortana) on their proselytization network

The Battle of Requiem was a series of skirmishes on the Forerunner shield world Requiem beginning on July 21, 2557. It was waged between the Prometheans occupying Requiem, Jul 'Mdama's Covenant forces and the United Nations Space Command. Shortly after the beginning of the battle, the Prometheans and 'Mdama's Covenant would join forces against humanity. These events marked the continuation of an ongoing conflict with Jul 'Mdama's Covenant and the UNSC, and the days following would see the conflict spread to Ivanoff Station orbiting Installation 03, and later the Prometheans would attack the human homeworld, Earth. Requiem would again become a battleground over six months after the initial battle in February 2558 when the UNSC launched a lightning-strike expedition to the surface of Requiem.

Background
"Humanity's loss of its biological form will serve as final payment for their crimes. It is a kindness they do not deserve."

- The Ur-Didact to Librarian.

In the final year of the Forerunner-Flood war, the Ur-Didact used a Composer—a secret massive Forerunner device capable of converting living beings into digital form that was long abandoned—in order to convert his loyal Promethean warriors into Promethean Knights to combat the Flood with risk of infection but failed due to their insufficient number. During the Flood and star roads' invasion of the Greater Ark while attempting to gain more additional Knight forces in his mechanized army once returned to the Requiem, the Didact took his personal flagship Mantle's Approach—supported by thousands of sentinels under his command—to Omega Halo, the youngest of dozen original Halo installations, and fired the Composer upon the ring to harvest the installation's entire human population that was the majority of the remaining human specimans of Librarian after moving from Earth. The Ur-Didact would serve the loss of biological form of human race by being forever imprisoned into digital form as the final punishment for defying the Forerunners earlier when the ancient mankind were used to be their rival until their downfall. He would also plan to eradicate what it remains in humanity along with every other "suspect" species that may treaten the Forerunners' hold of the Mantle to ensure that only the Forerunner would be worthly alone to hold the Mantle.

The loss of most of mankind and Didact's betrayal were determined to prompt the Librarian to have the Didact once again exiled into a Cryptum for the second time, now viewing the Warrior-Servant as a traitor by the IsoDidact for his genocide and also deserting the Forerunners. When the Didact was imprisoned by her wife in a "combat" Cryptum previously maintained on Mantle's Approach at the core of Requiem after being incapacitated by two shot from a Z-750 binary rifle, the Librarian hoped his husband would spend his time in meditation reflecting upon his past misdeeds, and that the damage wrought on his mind by the Gravemind would be corrected with the aid of contact with the Domain as the Forerunner Promethean constructs were taken over by the Librarian to prevent the Ur-Didact from being reawakened until his meditation would be complete. This would expect the Didact to halt his planned genocide against humanity and instead help his former foes ascend eventually to be the new caretakers of the galaxy by educating them on the Mantle and the Forerunners' technological achievements with the Janus Key. However, it was considered as a shocking failure to the Librarian after learning the Domain's true nature as a Precursor creation as well as the myhtical Organon, and that the activating of the final Halo Array would destroy the Domain along with all Precursor constructs by dismantling neural physics, ensuring the Forerunners' history being lost. As the Halo Array fired, Domain and the rest of the Precursor artifacts were destroyed, leaving the Ur-Didact being condemned to spend the next 100,000 years in complete silence, dwelling on his own insanity and rage.

Master Chief, Cortana and UNSC
"I'll drop a beacon, but it'll be a while before anyone finds us."

- Cortana to John-117.

Attempting to flee the incomplete Installation 08 faulty activated and destroyed to stop the Flood and end the Gravemind that resulted Installation 00 being severed after the last battle of the Human-Covenant War on December 11, 2552, managed to enter the Slipspace portal between the Ark and Earth that is still activated by the Portal at Voi as soon as it collapsed while inside it, cutting the frigate in half as a result. The aft half of the, carrying Spartan John-117 and AI Cortana, was transported to an unknown region in empty space shortly after escaping Installation 08 on a course toward Requiem with Cortana activated Forward Unto Dawn's emergency locator beacon while the Spartan entered cryostasis. With the last contact with UNSC being during the Battle of Installation 00 and only the Arbiter Thel 'Vadam aboard the other front half of the Dawn that was able to return to the UNSC-controlled space by crashing into Indian Ocean on Earth on December 23 after John-117 went cryo-sleep, John-117 who was honored as the humanity's greatest hero and soldier alongside Cortana were listed as missing in action like all Spartan-IIs that died during the Covenant War and presumed dead.

In 2556, Cortana, still stranded in unknown space alongside John-117 still unconscious, began to truly experience the effects of rampancy after seven years of age. She tried to communicate with the Spartan without response from him and also composing a history of Forerunners and of humanity and their wars since around one hundred millenium until 2552. She continued to become more and more unstable as more time passed. Despite her true rampancy state, Cortana already once experienced signs of rampancy when she was tormented by the Gravemind aborad the Flood-infested High Charity when John-117 returned to Earth via Anodyne Spirit to join the united UNSC-Sangheili alliance after failing to kill the Prophet of Truth. "A science team got zapped excavating a Forerunner artifact. This...sensor data is all that was left. And our geeks managed to pull some coordinates. I'll give you three guesses where it led."

- Captain Andrew Del Rio.

After being commissioned on February 21, 2557 known as the "Infinity Day",, now re-purposed for peace and exploration, was tasked with finding the remaining Halo Installations in order to etablish UNSC permanent bases for studying and decommissioning ancient galaxy-destroying ringworlds as the UNSC already managed to set up these bases on the glassed Installation 05 and Installation 03, the two first Halo rings discovered after the destroyed Installation 04. After the Infinity extracted a Composer from Installation 03 to transport it to Ivanoff Station, an ONI team were digitized by the Composer while studying and excavating the Forerunner artifact and subsequently, the sensor data from the incident contained coordinates of Requiem, allowing the crew of the Infinity to find the location of the shield world. Simultaneously, Commander Thomas Lasky picked up Cortana's distress signal from the Dawn and learned that John-117 was aboard the light frigate. He had a flashback as he remembered when he met the Spartan when the Covenant invaded Circinius IV in April 26, 2526 by saving him from a Sangheili Zealot and a Mgalekgolo, and was inspired by SPARTAN-117 to rise to the rank of Commander in the UNSC Navy. Preparing for the departure for Requiem and recover John-117 and Cortana, UNSC Infinity's crew entered cryo as Infinity, leading a moderate expeditionary fleet of s and s, jumped in slipspace.

Jul 'Mdama
"Requiem's treasures shall be ours."

- Jul 'Mdama after finding Requiem in 2554

Blaming the UNSC for being "correctly" the responsible of the death of his wife, Raia 'Mdama, Shipmaster Jul 'Mdama who was formerly part of the Servants of the Abiding Truth opposing the Thel 'Vadam's Swords of Sanghelios's peace with the Unified Earth Government vowed to seek vengeance against the humanity and etablish his new faction, an offshoot of the former Covenant going by the same name. In response, 'Mdama accrued a number of Covenant vessels to begin to amass a fleet sized enough to engage the UNSC Expeditionary Strike Group 1, with the traditional Song of Retribution being his flagship and of his faction and appointed himself as the Supreme Commander of his "Covenant".

Within the next two years after the end of the Great War in 2554, Jul 'Mdama led his fleet, including Song of Retribution and at least 3 other assault carriers, to Requiem in search of the shield world's "treasure": he sought the Didact, the leader of the Forerunner military, due to their mutual hatred of humanity. However, 'Mdama could not find a way into Requiem despite every attempts, so the Song of Retribution held station in orbit. On July 21, 2557, the Covenant fleet that accompagnied Retribution returned to Requiem via slipspace as the Dawn entered the planet's gravity well; 'Mdama sent his forces to board the frigate to keep any humans away. As his Covenant troops entered the ship, Requiem began to scan the Dawn for a "Reclaimer".

Opening skirmishes and Didact's awakening
"If you haven't mastered even these primitives, then Man has not attained the Mantle. Your ascendance may yet be prevented. Time was your ally, human. But now it has abandoned you. The Forerunners... have returned."

- The Ur-Didact to John-117, declaring the return of the Forerunners

Cortana awoke John-117 from cryostasis and informed him of intruders on the Forward Unto Dawn. When the duo found out that there was a former Covenant fleet around the Dawn and one of the s was moving into a intercept course, Cortana instructed John to fire one of Dawn's missiles at the cruiser. The Spartan battled through the wreckage and managed to destroy the cruiser moments before it fired its energy projector. While on the outer hull, John was scanned by a beam coming from Requiem, which then opened its interior for the Reclaimer. Forward Unto Dawn, along with several Covenant cruisers, was pulled into Requiem's interior. At least one cruiser was destroyed when a piece of wreckage from the Dawn impacted upon it as they were drawn into the shield world.

John-117 and Cortana survived the fall into Requiem's middle shell. They decided to hijack one of the surviving Covenant ships to return to Earth, where they would be able to find Dr. Catherine Halsey to assess Cortana's rampancy. However,, after picking up Forward Unto Dawn's distress beacon, was approaching the shield world. While looking for a way to contact Infinity, John and Cortana accidentally triggered Requiem's guardians, the Prometheans. The Prometheans attacked the Spartan as well as Jul's Covenant. In an effort the warn Infinity of Requiem's gravity well, the Spartan-AI team disabled two energy pylons inside Requiem's core in order to eliminate interference emitted from a satellite in the core. When John attempted to contact Infinity in the satellite, it was revealed that the Didact had purposely manipulated Infinity's signal to trick John-117 into releasing him from his Cryptum. The Didact openly declared war on humanity and resumed control of his mechanized Prometheans; viewing the Didact as a living god, the Covenant forces followed suit.

Infinity's arrival
"FLEETCOM, this is Infinity! We are encountering an unidentifiable gravimetric disturbance and are being pulled inside a planet of Forerunner origin! Possible contact with the UNSC Forward Unto Dawn!"

- Andrew Del Rio broadcasting an emergency transmission. As the Infinity and her fleet continued to approach Requiem, the ship's control systems were swiftly hacked by the Didact as Requiem opened again one of its portals and pulled the Infinity into the shield world, causing violent explosions inside the supercarrier as her approach went chaos with her parked vehicles crashing one another. John escaped Requiem's core just as Infinity entered Requiem's outer shell.

Infinity crashed into a jungle inside Requiem and was immediately attacked by Promethean and Covenant forces. During the attack, Infinity's commanding officer, Captain Andrew Del Rio, deployed Marines and SPARTAN-IVs for reconnaissance, believing that the Infinity would be able to fend off her attackers while providing support for ground forces. The ill-prepared Marines were overwhelmed by the unfamiliar Prometheans and suffered heavy casualties. In addition to losing their landing zones, many Pelican dropships were shot down. Infinity was eventually boarded, allowing the Didact to extract information about the Composer, a Forerunner superweapon, from the ship's mainframe. John-117 joined Commanders Thomas Lasky and Sarah Palmer just as Captain Del Rio recalled ground forces to Infinity. John cleared a landing zone for the UNSC forces and headed to Infinity's crash site. There, John-117 and a squad of SPARTAN-IVs broke through to one of Infinity's hangar bays. John piloted a Mantis assault mech and fought through Infinity's maintenance corridors to some of the ship's weapon systems. After John destroyed the Covenant jammers near the control terminals, Infinity disabled two CRS-class light cruisers and damaged the Didact's Cryptum, prompting the Forerunner to retreat. The repaired Infinity left her crash site, but since she was still under the effect of the Requiem's gravity well, Captain Del Rio sent John-117 and Gypsy Company to take down the Forerunner anti-air particle cannons near the gravity well generator.

At some point during the battle in 1604 hours, Cortana conversed the original shipoard AI of the Infinity, Aine, who was heavily damaged by by the time when the Infinity crashed for a dozen seconds, asking her for the help the ship's crew. However, Aine, noticing Cortana's rampancy that may kill even more of Infinity's crew and the deactivation of her central power core at Cortana's hands, declined. She subsequently threatened her with informing Captain Del Rio to lock Cortana and John-117 on the ship or articulate the Unified Earth Government's policy for final dispensation as Cortana continued to ignore advices from Aine. In response, Cortana accidentally broke down Aine's matrix, killing her as a result while the AI believed that Aine could have accepted the opportunity to let Cortana and John-117 helping the shipboard AI. The conversation was recorded as the "Cyroraeth Dialogue", and the story of the fonctional death of Aine was kept as secret to the majority of Infinitys crew, believing the former shipboard AI was terminated upon the Infinitys impact on Requiem.

Assault on the gravity well generator
"Priority is to free Infinity from Requiem's gravity well and file a threat assessment back at FLEETCOM."

- Captain Del Rio prioritizing the Infinity's safety to John-117

Gypsy Company, aboard a Mammoth and led by Commander Lasky, destroyed the first and second anti-air particle cannons. However, a Covenant Lich heavily damaged the Mammoth. Even though John-117 and a SPARTAN-IV team destroyed the Lich, the Mammoth was forced to stop when it approached a Forerunner structure.

John entered the structure and, with Cortana's help, disabled the last two anti-air cannons. Cortana suddenly disappeared, so John searched the structure for her. He was taken to an archived personality of the Librarian, the Didact's wife and the one who saved humanity from the Halos. The Librarian informed John of the Didact's plan to imprison humanity into digital form with the Composer. In doing so, she altered John-117's genes, an action that would prove itself useful when the Didact's forces raided Ivanoff Station. John-117 returned to a UNSC convoy led by Master Sergeant Marcus Stacker and eventually reached Requiem's gravity well generator. Using targeting data provided by the Spartan, Infinity destroyed the generator.

The Didact's departure
"Do you truly believe these theatrics can prevent my departure? Embrace your sad fate and retain your nobility - I am already beyond you."

- The Didact to Master Chief

Following the destruction of the gravity well generator, the Master Chief and Cortana began to push for Captain Del Rio and Infinity to assault the Didact's Cryptum and destroy it to keep the Didact from leaving Requiem. However, Del Rio refused to believe the two, calling their encounter with the Librarian "the hallucinations of an aging Spartan and his malfunctioning AI." This was furthered when Cortana's rampancy caused her to have an angry outburst. While Del Rio ordered Commander Lasky to remove Cortana's data chip to be destroyed, the Master Chief took it instead, telling Del Rio that if he wouldn't stop the Didact, the Master Chief would do it himself. The Master Chief refused Del Rio's orders to stand down and ordered Lasky to warn Earth of the coming threat from the Didact. Lasky was then ordered to prevent the Master Chief's departure by any means necessary but recognized that it was too dangerous to risk the Chief being wrong about the Didact. Instead, Lasky had a Pelican gunship prepared for full combat pursuit of the Master Chief but instead gave the dropship to the Spartan.

The Master Chief departed Infinity in the Pelican as Infinity and her crew made their escape from Requiem. Without Infinity's firepower to back them up, Cortana suggests instead disrupting the communications at two of the towers near the Didact's Cryptum which would allow her to forge an override code and lower the Didact's shields so they could reach him. Using the Pelican's cannons, the Master Chief was able to destroy the Phantom dropships guarding each tower and make his way within. Inside each tower, the Master Chief fought his way through 'Mdama's determined Covenant and Promethean defenders and used an EMP in one tower to destroy a carrier wave generator and destroyed the attenuators in another tower, giving Cortana the opportunity to lower the Didact's shields. All through this, the Didact telepathically taunted the Master Chief about the futility of his actions.

With the Didact's shields down, Cortana suggested another course of action: reach the tower that controlled the spires surrounding the Didact's Cryptum and use the controls to encase the Cryptum in the towers and keep it from leaving Requiem. The Master Chief returned to his Pelican gunship and used it to reach the third tower, encountering no further aerial resistance along the way. Inside the tower, the Master Chief came up against a massive force from 'Mdama's Covenant defending both levels of the tower including two Hunters and several Shade turrets and Banshees. The Master Chief was eventually able to reach the control panel where he inserted Cortana who took control of the tower system. Cortana initially moved the towers to imprison the Didact's Cryptum, but her rampancy got the best of her and instead she dropped the towers.

Unable to imprison the Didact any longer, the Master Chief decided to move across some nearby Liches heading for the Cryptum to reach the Didact. However, after he landed on the first Lich, the Cryptum merged with the Forerunner ship Mantle's Approach and joined a fleet heading out into space. Unable to stop the Didact from leaving, the Master Chief hitched a ride on the Lich as it followed the Didact's ship into slipspace.

Didact's plans
The Didact would arrive at Ivanoff Station and despite the efforts of the UNSC, he obtained the Composer and digitized pratically everyone on the station excluding John-117, who was saved thanks to genetic augmentations provided by the Librarian. The Didact then set course for Earth, with the intent of digitizing its population, but was ultimately stopped and defeated by John-117.

Requiem
With the Infinity and the Master Chief gone, Requiem remained under Promethean and 'Mdama's Covenant control. After leaving Requiem, Captain Del Rio was relieved of duty by the UNSC Security Council due to his decision to leave the Master Chief on Requiem, and Commander Lasky was promoted to captain of the Infinity.

The UNSCDF would not return to Requiem until six months later, when the Infinity was again deployed to the shield world to establish research bases and obtain useful Forerunner technologies, resulting a larger-scale but indecisive battle against Prometheans and Jul 'Mdama's Covenant which led the eventual destruction of Requiem along with rest of the Epoloch system.

Ground forces

 * UNSC Navy
 * UNSC Marine Corps
 * Bulldogs
 * Gypsy Company

Vehicles

 * M808C Scorpion
 * 0383
 * D79-TC Pelican
 * Pelican 595
 * ''Papa Foxtrot 766

List of appearances

 * The Commissioning
 * Scanned
 * Halo 4
 * Terminals
 * Spartan Ops
 * Halo: Escalation
 * Halo 5: Guardians
 * Halo Mythos
 * Halo: Fractures
 * Rossbach's World