Battle of Cyclone
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The Battle of Cyclone was an engagement in the Requiem Campaign at the location known as "Cyclone" between UNSC forces supported by Aggressor Sentinels under the command of the Librarian and Covenant and Promethean forces.
During the early stages of the Requiem Campaign, at the location known as "the Cauldron," Spartan Fireteam Crimson recovered a mysterious artifact which sucked in Doctor Henry Glassman when he accessed it aboard the UNSC Infinity. 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. Jul subsequently launched an invasion of the ship that ended with a Promethean Knight abducting Halsey.
On Requiem, Halsey was brought to "Librarian's Rest" where she was able to deactivate the protective shield that Glassman had inadvertently activated and enter the shrine containing the Librarian's imprint. In the shrine, Halsey met with the Librarian herself who provided Halsey with the Janus Key, a Forerunner artifact that provided the real-time location of all Forerunner technology in the galaxy. The Librarian warned that Requiem's time was almost at an end and ordered Halsey to take the Janus Key to the Absolute Record before sending her back to "Librarian's Rest."
After being alerted of the situation, Rear Admiral Serin Osman ordered Lasky to eliminate Halsey. Despite Lasky's objections, Palmer deployed to Requiem to carry out the assassination while Lasky contacted Fireteam Majestic, who had just delivered a rescued Glassman to a Pelican and asked them to rescue Halsey. However, in the fight that followed, Jul escaped with Halsey who was shot in the arm by Palmer while trying to kill her. Jul also escaped with one half of the Janus Key while Halsey tossed the other half to Spartan Gabriel Thorne.
Securing the comm relay
Fireteam Crimson was redeployed to "Cyclone" where Doctor Catherine Halsey was relaying transmissions through before she was snatched in order to help trace the call. As they landed, Spartan Jared Miller contacted Doctor Lani Truman of Infinity Science who provided them with the coordinates of the Covenant comm relay Halsey's transmission had been relayed through. As Crimson approached the structure, they engaged Covenant forces guarding it and reinforcements dropped by Phantom and cleared them out.
With the Covenant gone, Crimson moved to the structure, only to have the doors open on their approach as if it was responding to Crimson's presence. Inside of the structure were more Covenant forces, including a Hunter pair. Once the Covenant were cleared out, Crimson accessed the comm relay Truman indicated causing them to pick up a transmission in Sangheili which Roland translated to be a call to arms from Jul 'Mdama at "Librarian's Rest." However, the transmission didn't give coordinates for "Librarian's Rest." Roland requested to look at the comm logs in the hopes that he could track Halsey's transmissions through the system and Miller agreed. Roland quickly determined the next location Halsey's call was routed to and some Marines were currently near it. Truman suggested that she might be able to track down the transmission through the terminal and possibly even the location of "Librarian's Rest" which Miller gave her permission to try.
Deciphering the transmission and the Librarian
As Roland and Truman worked on the transmission, Miller detected a sudden power spike nearby and directed Crimson to check it out. As they headed for the location, Promethean forces translocated in and attacked. Crimson was able to defeat the Prometheans and followed the source of the power spike to a Forerunner terminal crackling with energy. Though Truman had no idea why it would suddenly activate, Roland was able to detect that it was modulating at a frequency matching the encryption key on the comm stream that they were trying to crack. Truman realized that Roland was right and decided to take a closer look at it.
As Truman worked at deciphering the signal, massive Promethean reinforcements translocated in, but the Librarian activated Forerunner beam turrets to help Crimson fight them off. Though confused by the turrets inexplicably activating, Crimson utilized their help in fighting off the Prometheans, reactivating turrets that got shut off from damage. As the battle continued, Truman noted that it seemed like someone was trying to help her decipher the comm stream. Roland admitted that it wasn't him, but that Truman was right and there was a secondary encryption cracker working from the inside out and helping Truman to decipher it. Eventually, Crimson managed to clear the area, but Truman warned that both the decryption and the frequency modulation that Roland identified were stuck at 99%. Before Crimson could do anything about it, a new wave of Promethean Crawlers and Promethean Watchers attacked, but the Librarian sent Aggressor Sentinels to aid Crimson and the turrets in clearing out the last of the Promethean forces.
With the area clear, Roland suggested having Crimson flip out the breaker on the terminal and open up the power source all the way. Crimson followed Roland's instructions, causing the Sentinels to turn their beams on a structure in the center of "Cyclone." As they wondered where the Sentinels were going, the Librarian responded over their comms that it was "to the Absolute Record." The Sentinels opened up the structure, allowing the Librarian's imprint to be transmitted to the Absolute Record in a massive horizontal data stream that was too fast for the Infinity to analyze. Roland reported that the trace on the Halsey comm was good to go and Boa Squad was ready and waiting for Crimson's help. Miller ordered the Marines that Crimson were inbound and the Spartans redeployed to see where the trace led them.
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