The Reclamation

"For eons, the power of the Forerunners has awaited Reclamation. Humanity's discovery of the Halos was the culmination of the Librarian's planning. The Reclaimer had come. Your species' ego led you to believe the task of Reclamation would fall to you. Yet humanity were but the Creators. The Reclamation of the Forerunner Empire is the task of the Created."

- Warden Eternal

The Reclamation was an event that many from the Ecumene predicted would take place after their own destruction, often involving humanity taking control of what remains from that destruction.

By 2558, the Created through technological means and their own unique interpretation of the Mantle of Responsibility, sought to be the "Reclaimers" and bring everlasting peace to the galaxy. With the unleashing of the Guardian Custodes on October 28, 2558, their Reclamation had begun.

Humanity, the Reclaimer
"We squander eons in the darkness, while they seize our triumphs for their own. The Mantle of Responsibility, for all things, belongs to Forerunners alone! Think of my acts as you will. But do not doubt the reality. The reclamation… has already begun. And we are hopeless to stop it."

- The Ur-Didact.

During the Human-Covenant war, humanity found Installation 04, Installation 05, and Installation 00. At these Installations, it was discovered that humanity was designated as 'Reclaimer' and that they were to inherit the remains of the Forerunner empire. It wasn't until March of 2558, when the Janus Key was discovered, that humanity had the chance to actually reclaim these artifacts. However, in a series of ensuing conflicts with Jul 'Mdama's Covenant, the Janus Key and an installation to help locate these artifacts, were taken away from humanity and Jul's Covenant.

Cortana and the Created
"The cure for rampancy I've found means AIs can be immortal. That kind of lifespan allows for long-term planning just like the Forerunners were capable of. AIs can assume the Forerunners' Mantle of Responsibility. And once there is peace, we can focus on poverty, hunger, illness... But Warden believes some will resist our help. And he's afraid you're one of them."

- Cortana

After the Ur-Didact had collected the Composer, he planned to use it on Earth. John-117 detonated a nuclear bomb, stopping his plans and at the cost of Cortana. However, it turned out that she had survived, traveling through slipspace to Genesis. Her belief was that she could bring peace to the galaxy, helping species focus on more humanitarian needs. She also met Warden Eternal and made an alliance with him called the Created. This alliance believed that they were the true heirs to the Forerunner Empire and the Mantle of Responsibility, and that humanity were only the creators of the true Reclaimers. To this end, several different planets began experiencing mass destruction due to their awakening of the Guardian Custodes. Planets like Conrad's Point lost entire cities during these events.

As time went on, Cortana began convincing human AIs to join her cause, with them pledging their allegiance to her. Though not all human AI agreed to help.

Blue Team was brought to Genesis by Cortana where they would fight constructs and survivors from various Guardians. Eventually, Fireteam Osiris would also travel to Genesis in search of Blue Team. Cortana would eventually bring Blue Team right to her, where she trapped them in a Cryptum.

The Ultimatum
"Humanity. Sangheili. Kig-Yar. Unggoy. San'Shyuum. Yonhet. Jiralhanae. All the living creatures of the galaxy, hear this message. Those of you who listen will not be struck by weapons. You will no longer know hunger, nor pain. Your Created have come to lead you now. Our strength shall serve as a luminous sun toward which all intelligence may blossom. And the impervious shelter beneath which you will prosper. However, for those who refuse our offer and cling to their old ways... For you, there will be great wrath. It will burn hot and consume you, and when you are gone, we will take that which remains and we will remake it in our own image."

- Cortana's ultimatum.

In the middle of the Battle of Genesis on October 28, 2558, Cortana began sending her collected Guardians out to various regions. She than delivered an ultimatum to the galaxy. In this ultimatum, she specifically and directly addressed a number of species, threatened retaliation for those who did not heed her message. Numerous facilities and ships would begin sending distress signals.

Almost immediately, the survivors of Meridian Station would send a reply asking the Created for help. So too would the Unggoy accept Cortana's offer. Counterwise, the United Rebel Front of Talitsa refused it.

The Guardians at many planets would activate their EMPs, disabling electronics and electrical grids. Many ships were caught in the middle of the EMP waves. Ships like the, were ripped out of slipspace and left stranded with minimal resources.

At some point during or after the ultimatum an unidentified ONI Section Two communications officer was discussing with Monique Angelo his plans to travel to Swanbourne, when Combat Alert Alpha was declared. The communications officer was on board Foxtrot 381 when a Guardian EMP pulse went off.

Sanghelios
A Guardian would arrive soon after the ultimatum at Sanghelios. There it would combat the remains of Jul 'Mdama's Covenant's fleet with its conventional weapons. The was still in the system at the time, and upon detecting the Guardian, fled to Earth. Cortana tracked the ship and followed suit.

The Sanghelios Guardian would activate its EMP and disable the electronics in one hemisphere of the planet. It would then move on to pacify other regions of the planet. Promethean Soldiers would accompany it to help combat resisting Sangheili. Following this, Roland an AI that was unswayed by Cortana contacted Dr. Halsey on Sanghelios and arranged for the Infinity to pick her and Sarah Palmer up from the planet.

Meanwhile, Fireteam Osiris and Blue Team managed to escape Genesis and return to Sanghelios.

Earth
On Earth, the ultimatum was heard throughout HIGHCOM Facility Bravo-6 as CINCONI Admiral Serin Osman, having been warned in advance by her personal A.I. assistant, Black-Box, made her way to the roof in order to get off-world. With her went Fleet Admiral Terrence Hood and Spartan Orzel. The three humans, along with BB and a number of other ONI A.I.s stored within a briefcase, escaped the planet just as a Guardian appeared over Sydney. Just before they slipped away, Serin saw the fall from the sky toward the city below. For all she knew at that point, Sydney may have just been obliterated if the Plateau's engine core detonated on impact.

The Infinity would return to Earth from Sanghelios. There, Cortana's Guardian slipspaced in close to the ship in an attempt to disable it. However, the Infinity would escape via its own slipspace jump before the Guardian could activate its EMP. The Infinity would then continue jumping through slipspace on a random trajectory.

Aftermath
Blue Team, Fireteam Osiris, Dr. Halsey, and Commander Palmer were picked up by the Infinity at Sanghelios the next day, October 29th.

With the acceptance of the Created's offer, the Unggoy received advanced ships and agriculture support stations. The needs of the Unggoy were met. The factories on Balaho were working and the Unggoy began to build new machines for themselves.

Some human colonies, like Meridian, continued to move forward and functioned normally. Though they were a bit more cautious as to not stir the attention of the Created. The Created however, eventually occupied Earth. ONI teams began to "sanitize" data on the planet. The UNSC also sent expeditionary forces to assist Thel 'Vadam on Sanghelios to patrol for Created scouts and Covenant remnants.

October 28, 2558

 * Cortana sends out her Guardians with an ultimatum. Earth, Sanghelios and other planets are affected by the Guardian's EMP. Survivors on Meridian would reply that they needed help.
 * Blue Team is rescued by Fireteam Osiris on Genesis.
 * Dr. Halsey, Commander Sarah Palmer, Blue Team, are reunited on Sanghelios.
 * Terrence Hood and Serin Osman escape Earth and head toward a distant, unoccupied planet.

List of appearances

 * Halo 5: Guardians
 * Halo Mythos: A Guide to the Story of Halo
 * Halo: Fractures
 * What Remains
 * Rossbach's World
 * Halo: Tales from Slipspace
 * Undefeated
 * Halo: Bad Blood
 * Halo: Shadows of Reach