Invasion of the UNSC Infinity

During the Requiem Campaign, the suffered an invasion by Jul 'Mdama's Covenant and Promethean troops looking to destroy the vessel and capture Doctor Catherine Halsey in order to further Jul's plan to acces the Librarian's personality imprint on Requiem.

Prelude
Six months after the Battle of Requiem, the returned to the shield world to set up research bases to study the Forerunner technology present while also fighting Jul 'Mdama's Covenant for control of the artificial planet. At the location known as the Cauldron, Spartan-IV Fireteam Crimson recovered a mysterious artifact which sucked in Doctor Henry Glassman when he accessed it aboard the. Subsequently, Doctor Catherine Halsey was brought aboard where she determined that the artifact was communicating information from the ship to Requiem.

As Halsey later attempted to understand the artifact, Jul 'Mdama utilized it to contact Halsey via her data pad to entice her into helping him, offering Halsey the truth about a great many things, including the Prometheans. As proof, Jul ensured that Fireteam Crimson retrieved "the Didact's Gift," a Durance containing the "soul" of a Promethean Knight who was originally a human digitized by the Composer during the New Phoenix Incident. Having provided proof, Jul further enticed Halsey by mentioning the Librarian, but Commander Sarah Palmer noticed Halsey's suspicious behavior and Captain Thomas Lasky had her arrested. However, Halsey subsequently escaped using an override code on Infinity's AI Roland and made contact with Jul whose identity she quickly deduced. Halsey offered Jul her help with the Librarian, but the communication was cut off by Roland who regained control of himself and alerted the ship's crew to Halsey's actions.

The invasion begins
As Doctor Catherine Halsey was about to be escorted to a cryo chamber on the orders of Captain Thomas Lasky, Jul 'Mdama started an invasion of the ship through the artifact that had been brought aboard the. Promethean boarders translocated in, surprising the Infinity's Marines, led by Commander Sarah Palmer, who were unprepared for such an attack. Despite their best efforts, the Prometheans were able to make it out of the hanger containing the artifact and into the ship's hallways. As Lasky retreated into an elevator with Halsey, he ordered all hands to battle stations to defend the ship. Palmer quickly ordered all Spartan fireteams to fall back to Infinity to help as well, even those performing operations on Requiem. To help prevent the Infinity from escaping, Jul used the artifact to tether the ship to Requiem using an interdiction web.

By the time Fireteam Crimson returned from an aborted operation in Apex, the Infinity was also under attack from several s as well as numerous Phantoms and Banshees which had used Infinity's hanger bays to deploy Jul's Covenant troops aboard the ship as well. With the Infinity's defenses unable to pick out Crimson's captured Phantom from all of the enemy targets, the Phantom was accidentally shot down by friendly fire and crashed into Bay 450 on Infinity.

Securing the hanger bay
After the crash-landing, Fireteam Crimson were ordered by Spartan Jared Miller to help the Marines in the hanger secure it from Covenant forces, including reinforcements arriving in Phantoms while Fireteams Kodiak and Avalanche were ordered to secure Fore Armory Twelve-Seven. Once the hanger was cleared of Covenant, Miller directed Crimson to the hanger bay door controls, but the door failed to close and another Phantom made it inside followed by a second Phantom as Miller attempted to fix the problem with the systems. Miller managed to restore Infinity's COM systems and reestablish contact with Palmer and Roland. Roland determined that the artifact was causing some ship-wide problems and ordered Miller to have Crimson power cycle the engineering level server room in the hope that it would restore control of Infinity's systems.

After the hanger was cleared, Crimson made their way into the hallways while Miller attempted to establish contact with Lasky without success. With Jul's Covenant having made it into the ship's hallways, Crimson encountered multiple firefights between boarders and Covenant troops and aided the friendly forces in killing the attackers. Reaching the server room, Crimson eliminated the Covenant forces inside and started the power cycle. However, Promethean Knights attacked and Crimson was forced to fight them off as the servers rebooted. Once the reboot was complete, Crimson restored the ship-wide data link, bringing Infinity's systems back online. However, Roland could not activate the hanger bay door controls as they needed to be activated locally after a power cycle.

Crimson fought their way back to the hanger bay through more Covenant and Promethean forces and found the hanger occupied by Jul's Covenant again. As the Spartans endeavored to clear out the enemy and close the door, Roland contacted Miller with a new mission for Crimson dealing with a threat that could destroy the ship if it was not stopped. Crimson eventually managed to clear the hanger bay and activate the controls which successfully closed the hanger door and sealed out the Phantoms. Miller then directed Crimson to the engine room to deal with the threat that Roland had detected.

Stopping the nuclear warheads
On the way to the engine room, Roland explained to Fireteam Crimson that the hostiles in the room were yelling about "holy technology" and "death to the heathens" while Miller stated that Crimson was the only fireteam in the area that he could count on. As Crimson fought through Covenant and Promethean forces once again occupying the corridor, Fireteam Lancer was dispatched to backup Fireteams Kodiak and Avalanche in Fore Armory Twelve-Seven. However, before Crimson could get far, Miller realized that Jul's Covenant were once again occupying the server room and redirected Crimson to take out the enemy forces as they risked his Covenant reopening the hanger bay doors. As they approached, Infinity detected unregistered fissible material and alerted EOD teams. In the server room, Crimson found a Sangheili Warrior setting up the warhead from a HAVOK tactical nuclear weapon which they realized came from the missiles Crimson had earlier found in "Cyclone." After Crimson cleared the server room of hostiles, Roland sent Crimson instructions that allowed them to successfully disarm the nuclear weapon.

With the threat neutralized, Crimson began to fight their way through Jul's Covenant boarders towards the engine room while Roland became concerned about his inability to detect the warhead and Sergeant Jaime Velasco sent a distress call that the engine room was being overrun before being cut off. As Crimson engaged Jul's Covenant occupying the engine room, an alarmed Roland detected another warhead and warned Miller and Crimson who cleared the area and disarmed the warhead which had a timer that was primed. As Crimson had killed a Sangheili carrying a cloaking remote, Roland realized that he couldn't detect the warhead because it had been protected by active camouflage. Guided by Roland who was able to detect the active camouflage once he knew to look for it, Crimson was able to fight their way through the engine room and disarm a total of six nuclear warheads, ending Jul's Covenant plot to destroy the Infinity with stolen nuclear weapons. However, while Crimson succeeded in clearing out Jul's Covenant defenders, Roland warned them that more hostile troops were on their way.

As Covenant reinforcements invaded the engine room, Miller directed Crimson to emergency bulkhead door releases that, when activated, could seal the engine room tight and prevent Jul's Covenant from getting in again. Fighting through them, Crimson was able to seal the five bulkhead doors and secure the engine room against further invasion.

Reactivating Infinity's guns
After the engine room was secured, an alarmed Roland informed Miller that Infinity's aft defenses had just gone down, leaving the ship defenseless against Jul 'Mdama's attacking Covenant fleet. With Aft Weapons Control close to the engine room, Miller dispatched Crimson to help get the weapons back online. Helping Marines fight off Covenant boarders, Crimson reached Aft Weapons Control and discovered that Jul's Covenant had set up three devices that had caused the guns' cooling systems to malfunction and shut down.

As word came that Fore Armory Twelve-Seven had been secured and the fireteams guarding it were being redirected to additional action stations, Miller ordered that Crimson destroy the devices jamming the guns. Fighting through Jul's Covenant forces guarding the area, Crimson managed to destroy the three devices, but the guns still failed to come back online. As Roland attempted to figure it out, Prometheans entered accompanied by Hunters. Finally, Crimson managed to eliminate the attackers and Roland directed them to the controls that would reactivate the weapons systems. With Infinity's guns reactivated by Crimson, the UNSC flagship destroyed at least one of the attacking s and resumed fighting off Jul 'Mdama's attacking Covenant fleet.

Securing the ship
With the ship on lockdown, the guns firing and the engine room secure, Miller ordered Crimson to aid in cleaning up the enemy stragglers. However, before they could leave the room, Promethean Knights, Crawlers and Watchers teleported in to attack. Crimson was able to clear out the Prometheans, but Miller warned them that there was heavy enemy movement nearby. Emerging into the hallways, Crimson engaged Jul's Covenant forces there, including an energy sword wielding Sangheili Zealot who was equipped with active camouflage. As Fireteam Lancer was redirected to aid Crimson in clearing out the stragglers, Roland warned of another - admittedly pitiful - attempt by the enemy to take the server room. Returning to the server room, Crimson cleared out the Promethean forces occupying it and made their way back through the enemy-occupied hallways to confirm that the lockdown on the hanger bay was still in place.

Upon arriving in the hanger, Crimson discovered that it was occupied by enemy reinforcements, but was able to clear them out. As it appeared that they had won, more reinforcements arrived, including six Hunters. Despite massive odds, Crimson was able to kill Jul's Covenant forces and secure the hanger bay. A pleased Miller announced that Crimson had secured that part of Infinity and they would win the invasion yet.

Kidnapping of Doctor Catherine Halsey
Racing through the chaos of the invasion, Captain Thomas Lasky and Doctor Catherine Halsey were able to link up with Commander Sarah Palmer and make their way to the Infinity bridge. Upon arrival, Lasky ordered Lieutenant James to take the Infinity far enough out of Requiem's orbit that the Prometheans couldn't teleport onboard, but James warned that the controls weren't responding and the ship was locked in position. Roland informed Lasky that the artifact was acting as a slipspace anchor holding the ship in place and preventing them from escaping. As Palmer angrily turned on Halsey for not getting them free of the artifact days before, a Promethean Knight teleported onto the bridge, knocked Palmer down and grabbed Halsey, using her as a human shield against Lasky. The Knight teleported away with Halsey and Palmer and Lasky realized that the entire invasion was for the purpose of capturing Halsey.

With Halsey in their custody and having suffered massive casualties, Jul 'Mdama's Covenant and Prometheans ended their invasion and the survivors retreated.

Aftermath
With Halsey having communicated with Jul 'Mdama and then been kidnapped by his forces, Captain Thomas Lasky reported on the situation to Rear Admiral Serin Osman of ONI. Enraged by Halsey's actions and her own unwillingness to follow her predecessor's advice, Osman ordered Lasky to assassinate Halsey against his objections. Commander Sarah Palmer set out to assassinate Halsey against Lasky's orders, though he sent Fireteam Majestic in an effort to rescue her.

Having been taken before Jul at the Librarian's Rest, Halsey was able to access the Librarian's personality imprint who offered Halsey the Janus Key and instructed her to go to the Absolute Record. When Fireteam Majestic arrived, Halsey provided Gabriel Thorne with one half of the Janus Key before being interrupted by Palmer's assassination attempt which failed as Jul escaped with Halsey and the second half of the Janus Key.

In order to invade the Infinity, Jul locked the ship into place using the Requiem slipspace artifacts to create an interdiction web. Following the invasion's end, Jul left the web active, trapping Infinity in Requiem's orbit. After getting what he believed to be the full Janus Key, Jul placed Requiem on a collision course with its sun which would prove fatal to Infinity which was still stuck in orbit. Using a map recovered from Gek 'Lhar and "Lockup," Doctor Henry Glassman was able to figure out a way to successfully free the ship of its anchor by having Fireteam Crimson and Fireteam Majestic deactivate the artifacts on the shield world, ultimately allowing Infinity to escape at the last minute.

List of appearances

 * Halo 4
 * Spartan Ops