2558

2558 was a year in the 2550s in the 26th century. It was the year the begins Spartan-IV deployments to Requiem in operations referred to as "Spartan Ops," beginning the Second Battle of Requiem in early February. The Battle of Ealen IV takes place in early March, the Battle of Ven III takes place in early May, and the Battle of Oban takes place in mid-July.

January
January 17 January 21
 * A simulated trial hosted by AIs Roland and Black-Box is held to allow Iona to attempt to prevent her rampancy-precipitated final dispensation. Afterwards, Iona is put into stasis while the simulation is examined by human scientists.
 * Avu Med 'Telcam is assassinated by SPARTAN-G059 on New Llanelli.

February
February 1–7 February 2 February 6 February 7 February 8 February 9 February 10 February 11 Unknown date February 14 February 18 February 21 February 25
 * Gek 'Lhar escapes the ONI detainment center Midnight Facility, resulting in several fatalities and a heightened threat condition at the facility.
 * The Charity Fun Run from the ship's stem to her stern takes place.
 * Spartan Gabriel Thorne is assigned to Fireteam Majestic.
 * UNSC Infinity leaves Earth orbit for her second tour at Requiem with the intent to establish research facilities on the shield world.
 * UNSC Infinity arrives at Requiem. Commander Sarah Palmer, leader of Infinity ' s Spartan contingent, sends various Spartan fireteams to its interior surface. Marine, Army, and Navy assets are also deployed. At 0500 hours, Operation: LAND GRAB begins, involving Castle, Domino, Ivy, Crimson, and Majestic. Fireteam Crimson is then deployed to help Marines destroy power cores, intended for short-range wireless distribution. This is done to stop Jul 'Mdama's Covenant from occuping building bases in the area. Crimson is ultimately successful. Majestic, likewise, is deployed to assist Marines in the initial assault on 'Mdama's Covenant forces in location REQ-931 with the intent of securing a location for a research base.
 * Operation: ALL-SEEING EYE: Fireteam Majestic is deployed for a reconnaissance mission to identify a possible location for base establishment as well as to gather data on any of 'Mdama's Covenant forces present.
 * At 1901 hours, War Games simulations aboard Infinity between numerous Spartan-IV fireteams conclude for the day.
 * Operation: CHATTERBOX: Fireteams Majestic and Crimson are deployed to locations REQ-814-B and REQ-814-D to remove 'Mdama's Covenant forces in order to allow the UNSC to establish a base at REQ-626-C. Majestic begins by destroying one of their communications arrays at REQ-814-D.
 * A monthly poker night takes place aboard Infinity, with the grand prize of priority seating on all of the ship's internal shuttlecraft and trams.
 * Operation: ACADEMIC: Commander Sarah Palmer directs Fireteams Majestic and Crimson to Requiem with instructions to assault one of 'Mdama's Covenant outposts and recover a Forerunner artifact. They are successful and the artifact is taken aboard Infinity. The device teleports Chief Engineer Henry Glassman to the surface of Requiem while he is investigating it.
 * Operation: THREE-CARD MONTE: Fireteam Majestic, with support from Fireteams Tower, Castle ,and Domino, is tasked with a search-and-destroy mission against 'Mdama's Covenant outposts at locations REQ-822-A, REQ-822-B, REQ-822-C, and REQ-822-D.
 * The prowler arrives at Requiem, carrying Dr. Catherine Halsey. Halsey is brought aboard Infinity and shown the mysterious artifact.
 * The Forerunner artifact scans Infinity ' s systems and begins transmitting data to the surface of Requiem, where the data is intercepted by Jul 'Mdama. Glassman is taken captive by Jul 'Mdama's Covenant and is ordered to activate the Librarian's shrine, though he is not successful.
 * Sangheili terrorist Parg Vol is assassinated by Fireteam Crimson.
 * Carlo Hoya finds a classified transmission meant for Halsey and gives it to Thorne.
 * Fireteam Crimson secure another Forerunner artifact, dubbed "the Didact's Gift". This device contains the memories of victims of the Didact's attack on New Phoenix six months prior. The processed human minds are to be repurposed as Promethean Knights. Spartan Gabriel Thorne is translocated to the Cauldron by the first artifact.
 * Dr. Halsey begins dialog with an unknown party who shares her interest in the Librarian. The intelligence is actually Jul 'Mdama, the Supreme Leader, who is manipulating Halsey into divulging vital secrets about the Forerunners. Halsey is apprehended after her unwitting communication with 'Mdama is discovered. Spartan Thorne rescues Dr. Glassman and the pair escape custody, with Gek 'Lhar tracking them down.
 * Dr. Halsey learns that John-117 is still alive. Infinity is boarded by 'Mdama's Covenant and Promethean forces who capture the doctor. They take her to the Librarian's "shrine", where 'Mdama awaits.
 * Gek 'Lhar catches up to Thorne and Glassman, and is killed when Fireteam Majestic arrive.
 * Admiral Serin Osman, head of the Office of Naval Intelligence, orders Captain Thomas Lasky to kill Dr. Halsey. Commander Palmer is to execute the order.
 * Lasky sends Fireteam Majestic to rescue Dr. Halsey and stop Palmer.
 * The Librarian gives Dr. Halsey the Janus Key, but Jul 'Mdama gets half of the key. Halsey gives Gabriel Thorne the other half before she is taken away.
 * Fireteam Crimson unknowingly helps send the Librarian to the Absolute Record.
 * Jul 'Mdama sends Requiem on a collision course with its sun, Epoloch.
 * Fireteam Crimson, as well as Fireteam Majestic and Commander Palmer, head to shut down two respective artifacts on Requiem that hold Infinity in place and are successful. While the shield world is destroyed, UNSC Infinity narrowly escapes the planet's slipspace conduit.
 * Dr. Halsey agrees to cooperate with Jul 'Mdama and his forces, stating that she wants revenge.
 * Infinity's Atrium Park Valentine's Dance is scheduled to begin at 2015 hours.
 * A "Saturday Night (Cage) Fight" is scheduled to take place aboard Infinity, with the Spartans of Fireteam Sydney participating.
 * Infinity Day, marking the one-year anniversary of the flagship's commissioning ceremony. Festivities aboard the ship are to include a speech from Captain Lasky and Infinity-themed cupcakes.
 * A chili cook-off organized by Master Chef Jonathan Lowell is scheduled to be held in Infinity ' s forward mess hall.

March
March 3 March 5 March 8 March 10 March 11 March 14
 * Captain Lasky and Commander Palmer are debriefed by the UNSC Security Council at HIGHCOM Facility Bravo-6. The committee expresses misgivings of Lasky's handling of the Requiem Campaign and the failed assassination and escape of Dr. Halsey. Fleet Admiral Hood later tasks Infinity to escort him and the Arbiter on a diplomatic mission to Ealen IV.
 * Three ONI prowlers tasked to monitor the Swords of Sanghelios carrier Shadow of Intent are destroyed. These losses are not reported to the UNSC Navy.
 * A Catalog unit receives a request of take control of the Forerunner ecumene made by an unknown entity bearing the Didact's sigil.
 * Battle of Ealen IV: Infinity arrives at Ealen IV. Lord Hood meets with Thel 'Vadam and the Jiralhanae Chieftain Lydus. While negotiating, the delegates come under attack from Covenant mercenaries working for a group of human insurgents, the New Colonial Alliance. The Spartan-IVs defend the ambassadors, who escape into a nearby parts depot.
 * Shipmaster Vata 'Gajat arrives on Ealen IV to personally oversee the attack, while the ambassadors escape through a series of tunnels leading to a fortified redoubt in which they could take refuge in. Captain Lasky orders Commander Palmer and the protection detail to escort the delegation to the redoubt, while he and Spartan Naiya Ray try to reestablish communications with the fleet above the planet.
 * As Fireteam Jackknife arrive at the redoubt, Vladimir Scruggs betrays his team, killing them and the alien delegates' bodyguards. He then informs Commander Palmer that it is safe to bring the delegates into the redoubt.
 * In orbit, the Sangheili and Jiralhanae ships begin to deploy forces against each other due to the ambiguity of the situation on the ground.
 * Lasky and Ray destroy the reactor generating the Covenant jamming signal, restoring communications.
 * After the ambassadors and their security detail arrive in the redoubt, Scruggs ambushes them and holds Hood at gunpoint. Palmer shoots Hood in the leg and, in the resulting confusion, confronts and kills Scruggs.
 * With the mercenaries bearing on the site in force, the ambassadors escape to Infinity aboard a Covenant cargo tug. Paul DeMarco sacrifices himself to cover the ambassadors' escape with Covenant AA guns.
 * Infinity rallies the Sangheili and Jiralhanae fleets, prompting 'Gajat's fleet to retreat.
 * A funeral ceremony is held aboard Infinity for the Spartans who died in the battle.
 * Lasky and Hood discuss the likelihood of a severe security breach in the UNSC's organization, surmising that Scruggs could not have been the one who leaked the location of the negotiations.
 * Lasky and Hood discuss enlisting Petra Janecek's help in rooting out the spy who betrayed the Ealen IV delegation; flag officer is uneasy with Lasky's decision due to a conflict between Hood and Janecek.
 * Lasky and Ray leave Infinity abroad a prowler in order to recruit Janecek.
 * Lasky and Ray meet with Janecek in Castiglione on Escala III. Petra agrees to help Lasky uncover the UNSC spy in return for information regarding the Master Chief.
 * Infinity is ambushed on a mission to rescue a damaged civilian freighter, Pilgrims' Pride. However, they come under attack by automated craft supposedly originating from the long-lost.
 * Petra Janecek, Captain Lasky and Spartan Ray travel to the Sangheili colony of Karava to uncover the identity of the UNSC traitor. Meeting Janecek's informant Zef 'Trahl, they learn that the traitor is Daniel Clayton, a former UNSC captain and the illegitimate son of Spirit of Fire ' s commanding officer (and Hood's mentor), Captain James Cutter.
 * The UNSC supposedly discover the whereabouts of Spirit of Fire using data from Pilgrims' Pride. Infinity sets out to rescue the older ship. Upon arrival at the Spirit's supposed coordinates near Oth Lodon, however, they find a Covenant battlestation manned by the New Colonial Alliance. Having lured Infinity into a trap, Captain Daniel Clayton fires on the UNSC vessel with the station's energy projector, killing executive officer Commander Bradley and paralyzing Fleet Admiral Hood.
 * Clayton orders 'Gajat to stop the Spartans who are en route to the station, but 'Gajat decides to destroy Infinity instead. Fireteam Majestic and Commander Palmer board and secure the station, then destroy 'Gajat's corvette with the energy projector. Clayton is apprehended and transported to Infinity.
 * The UNSC dispatch a trio of vessels to Oth Lodon to assist with repairs to Infinity and to monitor the captured space station.
 * Lasky and Ray return to Infinity. The captain insists that the recent ambush could have been avoided if he were present, though Palmer insists that Lord Hood is to blame.
 * Hood visits Clayton and asks him why Admiral Mattius Drake wanted to destroy Infinity despite his attempt to capture it five years prior. Clayton tells Hood the New Colonial Alliance is stronger than before and have agents on every colony, as well as Earth. Hood orders Clayton's incarceration at ONI's Midnight Facility, but Clayton insists that they will meet again and the UNSC will fall.

March 15 March 22 March 24 Around March 29 Unknown date
 * ONI is unable to find the trail of Atriox and the Banished, who have disappeared some time before.
 * After having a nightmare about the New Phoenix Incident, Gabriel Thorne discusses it with Tedra Grant. Grant suggest Thorne the possibility of returning to New Phoenix for its reopening to see if his nightmares stop appearing after a visit to the city. After Grant's insistence, Thorne accepts.
 * Eight months after the attack on New Phoenix, the city is lifted from its quarantine. The President of the UEG, Dr. Ruth Charet, presides over the reopening of the city.
 * Returning to New Phoenix, Spartan Thorne, accompanied by Grant, receives proper closure about his grandmother's death in the New Phoenix Incident.
 * The  is commissioned.
 * War photographer and journalist Benjamin Giraud is hired by ONI's Senior Communications Director Michael Sullivan to write an in-depth profile on the Master Chief. After a time, Giraud starts to sense something is off and began finding hints of cover-ups, then resolves to establish the truth and perhaps discredit the dark rumors associated with John-117.
 * Human-Sangheili peace talks on Biko are violently disrupted by Sapien Sunrise, a reactionary anti-alien movement. John-117 arrives to stop the terrorists, killing 19 bodyguards, nine of whom are confirmed Sapien Sunrise members. The Spartan escorts Outer Colonies ambassador Richard Sekibo and all but three of the alien diplomats off-world, though Sekibo soon dies from his injuries. The event is covered up by the UEG to make the Master Chief seem responsible for the attack. However, the Spartan is soon vindicated.
 * A signal is discovered by ONI after Dr. Catherine Halsey assisted them get into her archive. This later turns to ONI discovering the Guardian sigil.
 * Benjamin Giraud's findings regarding the Master Chief's past are publicly discredited by ONI and Giraud is imprisoned in Midnight Facility.

April
April 2 April 15-April 17
 * Archaeologist Nathaniel Palmer expresses optimism in his personal diary regarding the future of his team's research on Installation 00.
 * Roughly a month after the events at Oth Lodon, Infinity is fully repaired.
 * Around this month, the Keepers of the One Freedom enter into a temporary alliance with the Banished.

May
May 8 May 9-May 10 Unknown date
 * A UNSC spy drone investigates a former Covenant bioweapon research laboratory on Ven III.
 * Spartans Ray and Thorne are assigned to a secret mission to capture Ayit 'Sevi (whose identity is withheld from them), a Sangheili in possession of the bioweapon unleashed on Ven III.
 * Thorne is captured and Ray discovers a major hideout for Kig-Yar pirates. Consequently, Captain Lasky decides to intervene and has Infinity head for Ven III.
 * Arriving at Ven III, Infinity is met by the Kig-Yar pirate queen's fleet and an orbital engagement ensues.
 * One of Infinity ' s Longsword fighters destroys the pirate hideout with two HAVOK missiles.
 * Ray pursues the Sangheili agent and disables his Ghost outside the base. Before she can take any further action, a prowler lands nearby and ONI agents lead 'Sevi inside under Admiral Osman's orders.
 * Thorne is rescued by Fireteam Majestic and Palmer, and returns to Infinity.
 * Lasky and Palmer speculate that ONI intentionally had Infinity get involved in the mission so the Kig-Yar pirates would be eliminated, after HIGHCOM failed to get involved six months ago. They conclude that the incident with the bioweapon was set up by ONI and the Sangheili agent was working for them.

July
July July 15 July 16 July 17 July 18 July 19 July 20 July 23
 * Tensions between Sangheili and human colonists on Carrow erupt into open hostility.
 * Dr. Catherine Halsey makes a personal journal entry on her views on the Forerunners and their technology, her contribution to humanity's survival and subsequent condemnation by the UNSC, as well as her encounter with the Librarian on Requiem. Despite the UNSC turning against her, she remains determined to combine the halves of the Janus Key and take them to the Absolute Record to fulfill the Librarian's plan.
 * Oban is attacked by Jul 'Mdama's Covenant and his Promethean allies. Spartans and UNSC Marines successfully defeat 'Mdama's forces in Saviron.
 * Captain Lasky and Commander Palmer discuss 'Mdama's assault on Oban. Lasky points out Palmer's frustration to find Dr. Halsey and reveals he wants Halsey back in custody. Palmer objects to having Halsey brought back and expresses her to desire to eliminate Halsey instead.
 * Dr. Halsey and Jul 'Mdama use a Forerunner artifact to trap Infinity in an uncharted system, preventing the ship from making slipspace jumps. Halsey intends to force the UNSC to give her their half of the Janus Key by luring them on a local planet using an energy source emanating from the surface. Aboard Infinity, Commander Palmer decides to lead a Spartan team to investigate the source of the signal on the planet.
 * The crew of UNSC Infinity track the source of interference to an island on Aktis IV. Commander Palmer and Fireteam Majestic eliminate a small group of 'Mdama's Covenant forces protecting a Forerunner structure on the island.
 * Upon discovering an artifact within the structure that is seemingly compatible with the Janus Key, the UNSC half of the Key is brought down to the island. Having created the artifact to fool the UNSC at the suggestion of Halsey, Jul 'Mdama's forces prepare to ambush the UNSC aircraft carrying the Janus Key to take it for themselves.
 * A rogue splinter group of 'Mdama's Covenant shoots down the UNSC aircraft and takes the Janus Key half for themselves, with its leader, Sali 'Nyon, inciting a rebellion among 'Mdama's forces.
 * Jul 'Mdama's concealed fleet emerges from Aktis IV's foam ocean and engages Infinity and the UNSC ground forces. The Spartans and Dr. Glassman barricade themselves in the Forerunner structure.
 * After seven hours of conflict, Infinity remains engaged by 'Mdama's fleet over Aktis IV.
 * The Spartans and Dr. Glassman use the local teleportation grid to escape the besieged Forerunner structure. Palmer, Ray, and Thorne take a portal to the jungle, intending to locate Halsey, while Grant leads the rest of Fireteam Majestic and Dr. Glassman to the other end of the island where UNSC reinforcements have been deployed.
 * With Sali 'Nyon's rebellion ongoing in 'Mdama's Covenant ranks, one Sangheili of 'Nyon's faction becomes disillusioned with the rebellion, steals 'Nyon's half of the Janus Key, and offers it to 'Mdama's forces. Dr. Halsey personally travels to the planet to claim the Key.
 * Commander Palmer's team observe the Sangheili defector in the jungle and wait for Dr. Halsey to arrive in order to ambush her. A firefight subsequently ensues between the Spartans and Halsey's Sangheili escort.
 * Sali 'Nyon's rebellion is stopped by Jul 'Mdama and his forces, with 'Nyon captured and all his followers killed.
 * Palmer captures Dr. Halsey, but the doctor clouds Palmer's judgment momentarily and escapes. Palmer gives chase, only to be incapacitated by a Type-58 Harvester. Halsey contacts Jul 'Mdama and is picked up by a Phantom.
 * Aboard Infinity, Lasky converses with Palmer concerning the events on Aktis IV while two ONI agents demand an audience with her. Palmer informs Lasky that because of her failure, Halsey and 'Mdama are now in possession of both halves of the Janus Key.
 * Jul 'Mdama and Dr. Halsey recombine the halves of the Janus Key, pinpoint the location of the Absolute Record, and set course there.

July
 * The UNSC Infinity undergoes a full retrofit above Earth while undergoing repairs following the events at Aktis IV. Several modules constructed for its developing sister ship, the among other resources are redirected to supplant the Infinity and her subsystems. The Infinity returns to service after a month in drydock.

August
August 11
 * A shipment of a Warthog, three Mongooses, and five Pelicans is received on Meridian from a dealer nicknamed Bozo.

September
September 1 September 15 September 17
 * Fireteam Apollo is ordered to report to Infinity by this date.
 * Melody Azikiwe revives Gray Team from cryo, Thars 'Sarov fights Rojka 'Kasaan above the planet Carrow, and Hekabe begins his attack on Suraka.
 * Admiral Serin Osman briefs ONI officers about Operation: ATHENA. A five-member team consisting of Spartan Palmer, Spartan Thorne, Spartan Tanaka, Ayit 'Sevi, and Dr. Glassman is assembled to infiltrate Jul 'Mdama's fleet and relay the location of the Absolute Record for UNSC reinforcements.
 * The team stows away aboard 'Mdama's Covenant assault carrier Breath of Annihilation just before the fleet makes the jump toward the Absolute Record.
 * Jul's fleet exits slipstream space near a gas giant. While reaching their destination, multiple slipspace portals appear and damage several ships of the fleet, including Breath of Annihilation.

September
 * The UNSC Infinity receives a full systems upgrade as well as scheduled maintenance. In the process, several modules from the incomplete are used to supplant those on the Infinity, leading to the replacement of several non-essential weapon systems.

October
October 13: October 17 Within 72 hours of October 17 Before October 23 October 23 October 24 October 25 October 26 October 27 October 28 October 29
 * 0340: Ram Chalva is interrogated by KT-49683-9 about Rion and Spark's location.
 * Around this date, the Mark VII is used as the testbed for the [GEN3] improvements, but it remained uncertain if manufacturers would adopt the standards and cost accounting by the Unified Earth Government.
 * A Spartan-IV is assigned to the UNSC Infinity, with Spartans Gabriel Thorne and Tedra Grant being assigned to guide him.
 * The UNSC Infinity prepares to leave Sol system in the next 24 hours and assault Jul's Covenant in Kamchatka, Caspar system, as part of Operation: ANCHORITE.
 * By this date, news about the attacks on Ursa IV and Oban reach the UNSC.
 * Forerunner anomalies similar to those on Ursa IV and Oban occurred on Queen Anne VI, Adelaide, and Conrad's Point.
 * Fireteam Osiris, led by Jameson Locke, is deployed to Kamchatka to rescue Dr. Halsey after she contacts the UNSC and claims to have information regarding the Forerunner attacks. They encounter an ongoing battle between a contingent of Jul 'Mdama's Covenant and Promethean forces. Fighting their way through the chaos, they not only succeed in retrieving Halsey, but kill Jul 'Mdama in the process, dealing a crippling blow to his Covenant.
 * Followers of the Triad spread their beliefs on social media sites.
 * ONI agent Maya Sankar is paired with the AI Black-Box and reassigned to Conrad's Point under the cover identity of "FERO" (her alter-ego as an Insurrectionist demagogue). Her mission is to infiltrate the NCA forces in control of the colony and investigate the nature of the anomalies.
 * Blue Team is deployed on a mission to recover the ONI research vessel Argent Moon. After being contacted by Cortana, John-117 decides to go to Meridian in search of her, using the ONI prowler Acrisius, disobeying orders to return to Infinity. The other members of Blue Team follow him. Blue Team is subsequently declared AWOL.
 * Fireteam Osiris is given operation orders to apprehend Blue Team and the prowler they took, though capturing John-117 is priority.
 * 0833: Blue Team heads to Meridian Station and is recorded though several means.
 * Fireteam Osiris is deployed to Meridian to apprehend the AWOL Blue Team. The team arrives to find residents under attack by Promethean constructs. Osiris helps defend the colony and gains the favor of Governor Sloan, who points them in Blue Team's direction. Osiris confronts Blue Team outside a buried Forerunner Guardian, but John-117 subdues Spartan Locke and Blue Team boards the construct. As the Guardian emerges, causing untold damage to the colony, Osiris backtracks to the colony's space elevator and manages to escape the catastrophe. Meanwhile, the Guardian departs via slipspace to the Forerunner world of Genesis.
 * In the aftermath of the Meridian Guardian, five more human colony worlds experience a Guardian emergence, bringing the total to eleven.
 * Aboard, the AI Roland deciphers the destination coordinates of the Meridian Guardian. Dr. Halsey deduces that Osiris can follow Blue Team by inputting those coordinates in a dormant Guardian, one of which can be found on Sanghelios.
 * The Meridian Guardian arrives at Genesis. As more Guardians arrive, some inadvertently bringing along Jul 'Mdama's Covenant vessels in their wake, Blue Team is attacked by the Forerunner entity Warden Eternal, who decides Blue Team is a threat to Cortana. Blue Team defeats the Warden and makes contact with Cortana. She explains how she survived the New Phoenix Incident and has been convinced by the Warden that she is the Reclaimer, and that it is the "Created" (artificial intelligences), not humanity (the "Creators"), who are the true inheritors of the Forerunners' Mantle of Responsibility.
 * Evelyn Collins and Doc Cale, survivors of the Guardian emergence on Meridian search Meridian Station for rations and supplies.
 * John-117 is declared KIA by the Office of Naval Intelligence. ONI Section II Press Secretary Lieutenant Penelope Boren delivers the news of his supposed death to the public; in the announcement, she notably misspeaks the Master Chief's date of death as being October 27, 2560 instead of 2558. Commander Michael Sullivan later sends a message to Admiral Serin Osman apologizing for the mistake.
 * The Triad posts a series of brief videos taken from the helmet recorders of soldiers who were on Meridian at the time of the Guardian's emergence.
 * Infinity arrives at Sanghelios, which is besieged by the remaining members of Jul 'Mdama's Covenant. Fireteam Osiris lands on the planet to make contact with Arbiter Thel 'Vadam, and rescues him from a assassination attempt by 'Mdama's forces. Coordinating with the Swords of Sanghelios, Osiris locates a Forerunner Constructor, then aids in the Swords' assault on the Sunaion, the final stronghold of 'Mdama's Covenant on Sanghelios while the Constructor reactivates the Sanghelios Guardian. Despite heavy resistance from Promethean forces and the Warden Eternal, Osiris boards the Guardian just before it enters slipspace. Meanwhile, the Arbiter's forces eradicate the remnants of 'Mdama's Covenant.
 * As a glass storm batters a group of survivors in Meridian Station, Marquez begins to work on building a transmitter capable of getting a signal off-world.
 * The colony of Laika III becomes yet another casualty of an emerging Forerunner Guardian. Rogue ONI agent Maya Sankar broadcasts a warning about these events to the other colonies. Realizing that ONI will try to suppress the broadcast, however, Maya allows the Insurrectionist Bostwick to kill her in order to make "FERO" a martyr and draw more attention to the warning. The plan succeeds, and ONI is unable to contain the news of the colonies' destruction. Maya's body is recovered soon after her death and used by ONI to create an AI to allow for further analysis of her experiences.
 * Fireteam Osiris arrives at Genesis aboard the Sanghelios Guardian, fighting through confused troops of 'Mdama's broken Covenant and aggressive Prometheans alike to reach Blue Team with the help of Genesis' monitor, 031 Exuberant Witness, who opposes the Warden Eternal and Cortana's plans to subjugate the galaxy under the Mantle. Before Osiris and Blue Team can coordinate a plan, Cortana teleports Blue Team to her inner sanctum.
 * John-117 and Blue Team fend off a series of attacks from the Warden Eternal and confront Cortana. She reveals her intention to use the Guardians to enforce the Mantle and asks John to join her. He refuses, and she imprisons Blue Team within a Cryptum while she begins her campaign to establish the Created's control of the galaxy.
 * After Thel's victory against Jul's Covenant, a Guardian shuts down one of Sanghelios' hemispheres. Thel's forces hides on Nuusra.
 * As the Guardians depart Genesis, Fireteam Osiris attempt to free Blue Team. Although Cortana still controls Genesis, her imminent departure causes her to disconnect from the installation, giving 031 Exuberant Witness a window to retake it. Osiris helps the monitor regain Genesis and prevent Cortana from leaving with the Cryptum. Blue Team is liberated and returns with Osiris to Sanghelios, where they and the Arbiter, Dr. Catherine Halsey, and Spartan Palmer plan how to stop Cortana and the Guardians.
 * Thanks to Blue Team's and Fireteam Osiris' actions, Keeper-of-Tools manages to find Bastion's location.
 * Cortana arrives in Earth orbit aboard a Guardian, while the other Guardians and Created begin shutting down communications and electronic infrastructure on all human colonies. As Cortana's Guardian uses an EMP weapon to disable all of Earth's infrastructure and defenses, the makes an emergency slipspace jump and goes on the run.
 * Survivors on Meridian make contact with Cortana, who promises that "All will be dealt with in time".
 * Installation 00's failsafe measures prevent Cortana and her allies from being able to access the installation, closing the Portal on Earth in the process.
 * After passing The Precept's test on Erebus VII, Rion Forge and Spark find Bastion within the Orion complex. At the same time, Keeper arrives at the shield world, and, with Rion and Spark's help, manages to launch the Eden to another galaxy to start the Precursor's reseeding.
 * Spark is assigned as Bastion's caretaker, leaving the Ace of Spades and making a slipspace jump with the shield world to avoid being found by Cortana or her Guardians.
 * The UNSC Infinity arrives to Urs system to extract Blue Team, Fireteam Osiris, Dr. Halsey, and Commander Palmer from Sanghelios.
 * Captain Lasky requests John-117, Jameson Locke, Dr. Halsey, and Sarah Palmer on Infinity ' s bridge, while Veronica Dare, by ONI's orders, requests Edward Buck to reform Alpha-Nine, including Michael Crespo. After some initial resistance, Buck agrees.
 * is attacked by the Warden Eternal. The ship's crew broadcast a distress call which is answered by UNSC Infinity.
 * Buck and Dare travel to Balaho to extract Kojo Agu, and discover the Unggoy of the planet have joined the Created. After their failure to rescue the UNSC embassy' survivors, the three left the planet.

November
November 1 November 4 November 5 November 12 November 25 November 28
 * Dural 'Mdama reclaims leadership over the Servants of the Abiding Truth by killing Kurnik 'Nuusra.
 * On Myer's Moon, Rion Forge and Little Bit wait aboard the Ace of Spades for the rest of the crew. After being put to sleep by Little Bit, Rion has one last conversation with the Librarian, who reveals her plans to reseed the Precursors in another galaxy.
 * Power is fully restored to Paxopolis and all its research sites.
 * The Pax Institute reopens.
 * The Banished arrive at Installation 00 aboard Enduring Conviction. After killing the UNSC forces and researchers present on the Forerunner installation, they begin to collect resources and establish a presence on the Ark.
 * Nathaniel Palmer records his recollection surrounding the escape of fifteen people, including himself, from the attack on the Henry Lamb Research Outpost.

December
December 7
 * Teranus records a log for his captain, in which he express his frustration with the Sangheili aboard the Enduring Conviction.