Vale Citadel

Librarian's Rest was a location inside the Forerunner shield world Requiem. The Forerunner structure was situated near the area codenamed "Sniper Alley". It hosted a shrine inholding the Librarian's imprint and later became a major emplacement in the conflict opposing the United Nations Space Command to the reformed Covenant.

History
Near the end of the Forerunner-Flood War, the Librarian decided to betray her husband, the Ur-Didact, and imprison him in his Cryptum inside the shield world Requiem. Before leaving Requiem, she made sure to save there an imprint of her memories that would assist humanity on their path to the Mantle.

In July 2557, John-117 and Cortana, and later the, found themselves stranded inside the shield world. On a mission to free the ship from Requiem's gravity well, John-117 managed to reach the Forerunner structure. Contact with Infinity was subsequently interrupted. Aggressor Sentinels guided him to a console. As Cortana was deactivating the remaining particle cannons, she mysteriously disappeared. The Sentinels once again guided the Chief to another room, in which Cortana seemed to be standing inside a beam of blue light. He stepped into it, beginning a spiritual encounter with the Librarian's imprint. She revealed to him the ancient history of humans, her role in helping mankind, and that the Spartan represented the culmination of her plans. She then asked John to prevent her husband from retrieving the Composer, which would once again menace mankind. To grant him an advantage, she awoke the seeds of the Didact that were hidden in him, however she was not able to give him more information as the Didact had found them. After that, John regained consciousness outside of the shrine and exited the beam. He retrieved Cortana on a nearby plinth and proceeded to make his way through Promethean forces. He took an elevator and Cortana informed him that his bio readings were all over the map since his interaction with the Librarian. Now that the Chief was aware of the Didact's plan, he entered a translocation portal to exit the Forerunner strucutre and rejoined with the UNSC forces outside to achieve his current mission.

After the mission, John-117 tried to inform the Infinity of the Librarian's existence and the informations she gave him. However, Captain Del Rio did not trust him and Cortana, leaving them alone on Requiem. Later, after returning to Earth and halting the Didact's attack, the Master Chief proceeded to a debriefing of the events, providing the UNSC information of his encounter with the Librarian on Requiem.

In February 2558, the UNSC sent the Infinity back to Requiem, with one of its goal being to find the Librarian-AI that John-117 had encountered six months earlier. At some point, Copernicus Base was established inside the shield world for this very purpose. However, the science base and Fireteam Castle were overwhelmed by Jul 'Mdama's Covenant forces. The Sangheili managed to find Librarian's Rest, but no Covenant were able to enter the shrine. With the aid of a Forerunner artifact which was brought onboard the UNSC Infinity by its crew, 'Mdama managed to abduct Dr. Henry Glassman. The Covenant forced him to work on opening the shrine. They believed that the Librarian would gift them incredible bounties spread throughout the galaxy, such as weapons and ships.

Despite not having adequate equipment, Dr. Glassman managed to activate the shrine. While all the Sangheili were captivated by the shrine, Dr. Glassman managed to secretly escape the room. Jul 'Mdama touched the glowing sphere but was repulsed by an energy burst, as he was not identified as a Reclaimer. He then noticed Glassman's disappearance and ordered his troops to find him and punish him for his blasphemy. Outside of the Librarian's Rest structure, Glassman was caught by two Sangheili Storm who had captured the recently translocated Spartan Gabriel Thorne. Thorne regained consciousness and managed to neutralize the two of them. As Gek remotely activated Glassman's explosive vest, Thorne snatched it off and threw it to the incoming Sangheili squad that was after Glassman. The Sangheili Storm were killed while the humans managed to escape.

Jul 'Mdama had previously tried to communicate with Dr. Catherine Halsey in order to obtain information from her, but she had been put into custody since then. And now that he had lost the cooperation of Glassman, he was surprised that she contacted him herself. She proposed offering him her help, though the communication was shortly interrupted by Roland. After an attack conducted by Promethean and Covenant forces on the UNSC Infinity, 'Mdama managed to abduct Dr. Halsey. At Librarian's Rest, 'Mdama discussed with Halsey about Glassman's work there, but it appeared that Glassman had originally not intended to deceive the Covenant. Halsey used her data pad to deactivate the protective shield and unlock the shrine, which emitted a beam of light. She then proceeded to run towards it, despite 'Mdama wanting to be the one meeting the Forerunner inside. Inside the shrine, Dr. Halsey met the Librarian's imprint. The Forerunner welcomed her and showed her the two halves of the Janus Key. She activated it and explained that it was a device capable of locating every piece of Forerunner technology in the galaxy. She deactivated the key and handed the two halves to Halsey, asking her to bring it to the Absolute Record to help propel mankind. She then warned her that Requiem's time was at an end. When taking the key, Halsey was subsequently expulsed of the shrine.

During Halsey's conversation with the Librarian, Jul 'Mdama ordered all his troops to meet at Librarian's Rest. This communication was intercepted by Fireteam Crimson when they were on a mission to search for the source of communications Halsey had been relaying at Cyclone. Both Roland and Dr. Truman were unfamiliar with it, but Truman managed to decrypt Halsey's communication stream with the external aid of the Librarian. The UNSC would only be able to hear part of the conversation, namely "to the Absolute Record". The UNSC eventually managed to locate Librarian's Rest. Commander Palmer set course for the Forerunner structure with the mission to assassinate Halsey, while Captain Lasky ordered Fireteam Majestic to rescue the doctor from the Covenant. At the entrance of Librarian's Rest, Fireteam Majestic clashed with Sangheili Storm while Thorne managed to enter the structure. Inside, Dr. Halsey had been expulsed of the shrine with the halves of the Janus Key in hands. Jul 'Mdama took the red half, unaware of the blue half's existence. Thorne entered the room cloaked and killed a Sangheili. 'Mdama subsequently reached for Halsey, ordering his troops to kill the intruder. The doctor managed to toss her half of the Janus Key to Thorne, who caught it. Palmer entered the room, fighting the Covenant. Promethean Knights appeared on 'Mdama's order. Palmer tried to aim for Halsey but only managed to shoot the doctor in the shoulder. The rest of Majestic arrived in the room and a fight ensued between the Spartans and the Prometheans. Thorne and Palmer ran for 'Mdama, but the Sangheili managed to escape with a wounded Dr. Halsey as a Knight appeared and translocated them away. As all the enemies at Librarian's Rest were either dead or gone and the mission was a failure, the Spartans left the structure after discussing their contradictory objectives.

As the Librarian had predicted it to Halsey inside the shrine, Requiem was set on a collision course with its sun by Jul 'Mdama, who thought he had obtained what he wanted and was willing to sacrifice the shield world in order to eliminate the humans. However, the Infinity narrowly managed to escape its destruction and both the UNSC and the Covenant eventually ended up with a half of the Janus Key. Librarian's Rest and the shrine containing the Librarian's imprint were destroyed alongside Requiem when the shield world collided with its sun, Epoloch.

List of appearances

 * Halo 4
 * Spartan Ops