Requiem Campaign

The Second Battle of Requiem was a large-scale engagement fought on the Forerunner shield world Requiem in February 2558. It was waged between the Prometheans and their Covenant religious followers and the intruding UNSC Defense Force.

Background
Six months before the onset of the battle in July 2557, the Forerunner Promethean supreme commander known as the Didact had been inadvertently awakened from his Cryptum on Requiem and immediately initiated a campaign against humanity, which he saw as unworthy of taking on the Mantle. Revering the Forerunner as a living god, revived Covenant faction under the leadership of Jul 'Mdama allied themselves with the Didact and his mechanical Promethean armies. The Didact was eventually defeated by Spartan John-117 above Earth, leaving the Prometheans without a leader, yet still hostile to humanity. The Prometheans and the Covenant continued to occupy Requiem, which humanity recognized as a site of great value due to the abundance of Forerunner artifacts contained therein, particularly a digital personality impression of the Librarian encountered by the Master Chief during the initial foray on the shield world. As a result, the, the most advanced warship in the Navy, was dispatched to establish research facilities on the Forerunner construct and eliminate any opposition from the occupying Promethean and Covenant forces.

Infinity ' s return
In February 2558, UNSC Infinity returned to Requiem. s were deployed to protect the ship and establish a position in orbit. Spartan-IV fireteams were sent into Requiem to support the UNSC Marine Corps, Armies and Air forces. UNSC forces set up several research bases: Copernicus Base, Galileo Base, and Magma Base. Other locations, such as areas designated "Quarry", "Fortress", and "Apex", were often contested for control.

During an interception on a Covenant archaeological dig, Fireteam Crimson discovered one of the three Requiem translocation artifacts on Requiem in "the Cauldron". The artifact was brought onboard Infinity, where it was examined by Henry Glassman. Glassman, who accidentally activated it, was translocated to Requiem and became a prisoner of the Covenant remnant. There, he was brought to Jul 'Mdama and was forced to find a method to activate the device containing the Librarian AI. Captain Lasky requested Doctor Catherine Halsey to be brought onboard Infinity to study the translocation artifact. Halsey found out that the artifact was communicating with the ship's system's, notably the engine, and transmitting signal to a location in Requiem. On Requiem, Sangheili Parg Vol, an associate of 'Mdama, was hunted and eventually assassinated by Fireteam Crimson.

Jul 'Mdama's plan
During their flight to Copernicus Base, Fireteam Castle was shot down by Covenant forces led by Jul 'Mdama. This attack drew Infinity 's attention to hunt down 'Mdama. UNSC scientists had discovered that the Covenant remnant are using Requiem's portal systems, and Fireteam Crimson was deployed to assist in the investigation. Incidentally, 'Mdama was detected traversing through the portals, so Fireteam Majestic and Crimson were sent to give chase. After discovering a way to activate Requiem's portal systems, Crimson followed 'Mdama to "the Cauldron", where he purposely left an artifact known as the "Didact's Gift" for Crimson, prompting the team to bring the artifact to Galileo Base. The Covenant remnant then staged an attack on the base to show that they were attempting to recover the artifact. While Fireteam Crimson defended the base, Fireteam Majestic extracted the "Didact's Gift" and brought it back to Infinity, where it was analyzed by Halsey. By giving Halsey the "soul of a Promethean Knight", 'Mdama had gained Halsey's interest in cooperating to find the Librarian. Their partnership, however, was discovered by Captain Lasky and Commander Palmer, who then took Halsey into custody. Spartan Gabriel Thorne, during his examination of the translocation artifact, was taken to Requiem like Glassman. On Requiem, the Covenant and Promethean forces attacked UNSC research bases "the Refuge" and Magma Base, but both of these attacks were successfully repelled by Fireteam Crimson (with the assistance of Fireteam Shadow in "the Refuge"). During their search for Spartan Gabriel Thorne in "Quarry", members of Crimson were captured by Covenant forces.

Spartan Thorne was captured by the Covenant and was brought to where Glassman was. Glassman, on the other hand, managed to activate the Librarian's device, and used the opportunity to escape. Glassman's escape distracted the Sangheili who took Thorne prisoner, giving Thorne the chance to retaliate. Together, the duo ran away, heading for Galileo Base, being chased by a vengeful Gek.

Second Attack on the Infinity
Meanwhile, as Dr. Halsey sat in the brig of the UNSC Infinity, Roland arrived and asked why she attempted to communicate with an unknown intelligence about classified material. After a brief interchange, Halsey used the pass-phrase override "undid iridium" to gain control of the A.I. and then use him to move unsuspected to the captain's ready room. Once there she perused all the material she could find for information on the Librarian and Jul 'Mdama, also discovering that John-117 was still alive and had survived the destruction of Installation 00. She then used the terminal to communicate with Jul 'Mdama. She offered her assistance in exchange for what they both wanted: the Librarian's secrets. At that moment though Roland regained control of his confused matrices and pulled the plug, and alerting Lasky. Just as the captain was about to have Halsey interred in a cryo-tube, alarms sounded across the ship: the Prometheans had gained access to the Infinity and taken all hands by surprise. Most Spartan and Marine fireteams were deployed on Requiem and the Prometheans quickly overran most of the ship. All UNSC assets were recalled to the ship, but at that moment the rest of the Covenant remnant fleet arrived, composed primarily of CRS-class light cruisers, and attacked the Infinity.

At this point, Fireteam Crimson reached the battle, still in the captured Phantom. Infinity's automated point-defense turrets could not differentiate between the thousands of incoming enemy spacecraft and Crimson was hit. Lieutenant Murphy barely guided the out-of-control dropship into one of Infinity's hangars, the bay's vacuum shields decelerating the dropship enough to allow all of its passengers to survive. Fireteam Crimson promptly went to work, clearing the hangar and locking down all bay doors on the port side of the ship, preventing further Covenant boarders. At that moment though, teams on board made two discoveries: the Covenant had internally disabled the all port defenses, leaving Infinity open to attacks from the Covenant fleet, and that the Covenant had UNSC nuclear devices with them from Parg Vol's supply and had armed the devices at key points throughout the ship. Fireteam Kodiak disarmed the nukes in the ship's armory while Fireteam Crimson disarmed the nukes in the engine room. With the nukes disarmed and back in UNSC control, Crimson re-activated the ship's port defenses, which promptly destroyed all adjacent ships. The remainder of the Covenant fleet fled as the UNSC re-grouped. But the Infinity was not safe yet. As Lasky escorted Halsey to the bridge, it was brought to his attention that Infinity was unable to move from its current spot because it was trapped by a sort of Slipspace anchor. As he turned his back, a Promethean Knight appeared, knocked Commander Palmer to the deck, grabbed Dr. Halsey, and disappeared again.

As the massive battle waged hundreds of miles over their heads, SPARTAN Thorne and Dr. Glassman trekked through the dusty canyons near Sniper's Alley to reach Galileo Base. Glassman sat down to take a rest and Thorne stopped to glance around. Realizing that something was amiss, he told Glassman to get to safety just as Gek emerged from invisibility, swinging his Energy Sword and slicing Thorne's Storm Rifle in half. Gek tossed Glassman aside like a ragdoll and attempted to truncate Thorne, who disarmed him in the process. Thorne managed to knock the Elite assassin to the ground. The Spartan then tried to break Gek's skull with a boulder, but the Elite caught it, flipped Thorne to the ground and brought the stone down on his chest, stunning him. Glassman was attempting to reach the fallen Energy Sword, but was stopped when Gek stepped on his outstretched arm, breaking it. Just as the Elite was preparing to execute the downed Spartan, he was shot in the head three times by DeMarco, who had shown up with the rest of Majestic. The Spartans looted his body, then returned with the injured Glassman to an LZ for Pelican evac.

The Janus Key
With the abduction of Dr. Halsey by enemy forces, Admiral Serin Osman, head of ONI, ordered Lasky to assassinate the doctor before the Covenant glean any sensitive intel from her. Sarah Palmer was deployed from Infinity despite Lasky's admonishments to the contrary. As soon as she was out of earshot Lasky contacted Fireteam Majestic and asked them to rescue Dr. Halsey, without telling them that Palmer was en route. The Spartans returned to the Covenant's base and engaged the sentries outside while Thorne used his recently-acquired cloaking unit to slip inside. At the same time, Dr. Halsey unlocked the shield set up by Glassman and entered the Librarian's shrine. Inside she was greeted by the Librarian's imprint, which presented to her the two pieces of the Janus Key, an artifact that would reveal the location of every piece of Forerunner technology in the galaxy. Once she reappeared outside the shrine, Jul 'Mdama snatched one of the halves away from her, not noticing the second piece in Halsey's hand. At that moment Thorne broke a nearby sentry's back, killing the other with his assault rifle. Halsey tossed the other half of the Janus Key to Thorne. Just as a sword-wielding warrior was about to kill him from behind, it was felled by Palmer. A pair of Promethean Knights appeared to protect 'Mdama and Halsey, but not before Palmer shot the doctor in the left shoulder. The rest of Majestic appeared and fought through the army of Prometheans alongside Palmer. Before they could reach the cornered 'Mdama, a Knight appeared and teleported away with him and the injured doctor.

List of appearances

 * Halo 4
 * Spartan Ops