From Halopedia, the Halo wiki
During the Requiem Campaign in 2558, Jul 'Mdama's Covenant used this location as a supply depot, storing a large amount of Covenant and UNSC weapons within the central structure's vicinity. After learning about it from a central intel center in the "Warrens," Fireteam Crimson was sent in to destroy the plasma stockpiles, and in the process, the Spartans discovered discarded HAVOK nuclear missiles. However, the warheads were removed. Fireteam Crimson was then extracted to assist Fireteam Switchback. It was later discovered that the removed nuclear warheads were taken to be used in an attack on the UNSC Infinity.
The Covenant forces later retook the area and placed three plasma artilleries in this area, allowing them to provide support to nearby troops. Fireteam Crimson and Fireteam Kodiak were sent in to neutralize these artilleries which were shelling Fireteam Majestic's position and pinning them down. The Spartans were able to destroy the heavily-shielded artillery pieces by targeting their power conduits and fought off a Covenant counterattack. The Covenant were aided by a Covenant listening post at "Lockup" using a downed Pelican to listen in on Spartan communications, but the defense and counterattack failed and both fireteams were extracted from the area.
After the abduction of Dr. Catherine Halsey, Crimson was redeployed to "Cyclone" as Halsey had been using it to bounce her transmissions around. "Cyclone" had once again been retaken by the Covenant, but the force guarding the area was much smaller and less heavily armed than on the previous occasions, and were eliminated without much trouble. At the same time that Crimson was in Cyclone, the Librarian's imprint was attempting to use a structure in the area to transmit herself to the Absolute Record. As Roland hacked the comm terminal in search of Halsey, the Librarian aided him in decoding the information and deployed beam turrets and Aggressor Sentinels to aid Crimson in fighting off attacking Prometheans. Both the decoding and the Librarian's transfer got stuck at 99% until Crimson opened up the breaker on the power source in the area. Roland was able to track the bouncing signal to "Control" while the Sentinels used their beams to open the structure in the middle of the area. In the form of a massive stream of energy, the Librarian's data stream was transmitted from Requiem to the Absolute Record. Dr. Lani Truman was able to tell that the stream of energy was a massive data stream, but it was moving too fast to analyze, while the Librarian announced that it was going to the Absolute Record. With Halsey's transmission traced to "Control," Crimson was extracted from the area by Pelican.
At some point, the UNSC had documented this area into UNSC Infinity's simulation combat deck for Spartan-IV training.
Cyclone is the location for the multiplayer map Vortex, making Vortex the third multiplayer map to be featured in Spartan Ops.
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