From Halopedia, the Halo wiki
Keeper was part of the Librarian's crew during the expedition to Path Kethona around 98,395 BCE. He was a young, ambitious Builder who was being groomed to move high in Forerunner society; this was suspected to be the reason he was chosen to be part of the crew of the Audacity. He devoutly attended the clandestine rituals of Builder secret societies, though he was still in the earlier phases of induction into their secrets.
After the first slipspace jump toward Path Kethona he noted that they had gone farther than any other Forerunner and praised the Audacity. He reacted to the presence of ancient Forerunner and Precursor artifacts within Path Kethona with great enthusiasm, taking this as evidence of cooperation between the two millions of years earlier.
Keeper-of-Tools did not accompany the Librarian planetside after the crew discovered a world home to primitive Forerunners who had been isolated from their brethren in the Milky Way for ten million years. After the Librarian had found out the truth of the origins of the local Forerunners, Audacity and her crew returned to the ecumene, although the Librarian would not reveal what she had discovered until much later.
Work on Bastion
Following the Audacity's return, Keeper works with Birth-to-Light, Dawn-over-Fields and Clearance-of-Old-Forests on Bastion to recreate the Precursors, building the Eden to transport the seeds of the race outside of the galaxy when the time is right.
Upload to the Domain
In the final days of the Forerunner-Flood war, Keeper, Birth, Dawn and Clearance were sent to to be the caretakers of Bastion, but the Flood's advancement through Forerunner space changed things. The four Forerunners are waylaid time after time, cast into one battle after another and constantly evading capture. Knowing that their work on Bastion was too dangerous to fall into Flood hands, the four upload their essences into the Domain until the war is over and the way to Bastion can be achieved in secrecy and safety.
To enact this, Keeper sought the help of an ancilla to procure a durance for him, which would allow the uploading of his mind to the Domain. However, the firing of the Halo Array nearly destroys the Domain, trapping and separating the four and possibly destroying the imprints of Birth, Dawn and Clearance.
After the Domain is accessed by Cortana on Genesis, Keeper awakened and emerged on the planet to discover that it had been compromised and that a thousand centuries had passed. He discovered that Bastion had been moved from its original location, a feat he believed would require "an impossible act of reconciliation" to perform. Keeper eventually surmises that the shield world's safety measures had been activated at some point in the past. He eventually found out that the Domain had been severely damaged by the Array, and was trapped on Genesis, degrading over time.
Surviving in Genesis' systems, Keeper witnessed the beginning of the alliance between Cortana and the Warden Eternal, and reacted with alarm as they took control of Guardians across the galaxy to enforce the Mantle of Responsibility. He noted, however, that the Domain had repaired itself enough to cure Cortana of her rampancy, and hoped to finally access it. Eventually, Cortana noticed his presence in her network and began to hunt him down, though Keeper left audio logs scattered across Genesis to warn the human forces who opposed her, noting that Cortana had not yet taken control of the installation's Constructors, and that the installation's monitor, Exuberant Witness, could use them to take back control.
As Cortana began to deploy her massed Guardian forces across the galaxy, and the Warden was distracted fighting both Blue Team and Fireteam Osiris, Keeper was able to finally access the Domain, restoring him and finally allowing him to locate Bastion.
As the Created conflict begins, Keeper is finally able to transmit his consciousness into a monitor body on Bastion after the arrival of Rion Forge and 343 Guilty Spark momentarily opens the shields and broadcasts a signal that Keeper is able to lock onto. Keeper calls Spark's choice of an armiger body "unfortunate" and states that they must move Bastion before his signal can be followed by a Guardians. Spark reveals Cortana's uprising to Rion, explaining that he had been detecting signals for weeks that he only now understood was a call to arms for the Guardians.
Keeper leads the others onto a gondola heading for the Nursery and declares that he and Spark are quite similar as both of their eyes have been closed only to open a thousand centuries later with much having been lost. Spark recognizes Keeper's loss and realizes that he is a direct imprint or essence of the real Keeper-of-Tools and Keeper explains his story to Spark.
Keeper leads Rion and Spark to Eden a starship that he had built modeled after the Audacity in the Nursery. Reaching the bridge, Keeper explains that the ship was meant to carry an extraordinary payload at the Librarian's bequest when the time came. Keeper refuses to answer what Eden's purpose is, stating that it is not for him to say and he needs Rion's key to initiate the launch as Eden's departure is long overdue and Keeper must complete his mission.
As Rion and Keeper start the launch sequence, Keeper communicates with Spark inside of his head, stating that he doesn't trust the human. Although Spark points out that Rion was led there like him, passing the Precept's test, Keeper calls it a last resort since the key was originally supposed to have been brought by the Librarian herself. Keeper suggests that the Librarian had planned for this as one of many possibilities, speaking of the Librarian as though she is not gone. However, Spark recognizes that Keeper is not accustomed to this new reality in which the Librarian no longer exists.
Keeper then explains that Bastion has need of an ancilla, having always been intended to be administered by three complete and unique ancillas like Spark. However, the monitors that had greeted Spark and Rion upon arrival are only indirect copies of the Audacity's crew and could potentially be swayed by Cortana which would be dangerous given that Bastion is the Librarian's laboratory containing her most dangerous research and experiments and Keeper believes that Spark had good reason not to be swayed by Cortana's promises.
As the ship's reaction drives come online, Spark questions where Keeper will go and if he will come back. Keeper states that he will go beyond this galaxy and has nothing and no one to return to. Keeper programs the gondola to take Rion and Spark back to the tower, having already sent his key there to give Spark control over Bastion. Addressing Spark as Monitor Chakas, Keeper states that he knows more about Spark than he knows and welcomes Spark home. Keeper gratefully returns the Librarian's key to Rion and Spark asks Eden's purpose is. After a moment, Keeper simply states "atonement" before departing the galaxy with Eden.
List of appearances