Some time after its construction, Installation 07 was stolen by 032 Mendicant Bias as a result of induced rampancy. This rampancy was onset through conversation with a being known as the Primordial, that was detained on the installation for interrogation. The Installation received its first activation above the San'Shyuum Quarantine worlds to eradicate their rebelling populaces. Two humans, Chakas and Riser, were deposited on the surface of the ring world after being torn from the ship of their Forerunner companions, Bornstellar and the Ur-Didact, who were dropped to the besieged world below.
Its diameter was originally 30,000 kilometers, until it was nearly destroyed after a failsafe collision course orbit with a Failsafe Planet. Its collision course with the Failsafe Planet was enacted by rogue Lifeworkers and presumably the Master Builder in order to stop 032 Mendicant Bias, in the event they failed or finished finding a cure for the Flood on the Installation. The cure was thought to be hidden in the genetic memories of humans, and they were also observed showing immunity to the parasite as well. Thus, 032 Mendicant Bias enacted a plan to save the installation for the eventual use of eraticating the Forerunners. After 032 Mendicant Bias was defeated in his plan, the IsoDidact, out to save the life stored on the ring's interior, arrived and ejected the damaged sections of the Halo in order to reduce its mass allowing it to transition through a small slipspace portal, necessary due to Installation 07's severely drained power supply. This reduced Installation 07's diameter to 10,000.
The installation survived the Forerunner-Flood War and was present at the Lesser Ark as one of the final seven when they were deployed for the final time. At the command of the IsoDidact, this Halo was sent through the portal containing the (presumably) Flood-infected Forerunners processed by the Composer, the timelocked Graveminds (of which approximately ten had already developed), as well as any remaining species infected or otherwise; to remain untouched as a sacred tomb "to millions" for approximately the next one hundred and one thousand years. After arriving at their final designated coordinates in the galaxy, under the command of the IsoDidact, the seven installations fired in unison to eradicate all sentient life in the galaxy, successfully containing the Flood parasitic lifeform.
In 2552, during the Battle of Installation 05, a signal was sent to this Halo from Installation 05, putting it on standby mode. A readout from Installation 05's Control Room showed that Installation 07 was fully prepared to fire on demand.
A more comprehensive readout was later observed on the Ark during the Battle of Installation 00 by Thel 'Vadam, John-117 and the Prophet of Truth, once again displaying that Installation 07 was on standby mode, waiting to receive the signal to fire. However, John-117 deactivated the installation before it was able to finish its activation sequence.
In 2555, while exploring the Shield world Trevelyan, archaeologist and Forerunner cultural expert Luther Mann discovered records buried deep within its vast information pathways and proceeded to translate them. The information he uncovered revealed the location of Installation 07. By 2558, the Swords of Sanghelios contained and sterilized a Flood outbreak within an infection zone on the ring. Once the UNSC assessed this information, they joined with Sangheili fleets to monitor the installation to make sure the Flood didn't return to the site.
- This ring is often confused with Installation 01's holographic projection on the Ark because it is the first ring from the entrance to the Citadel. Although, it is in fact the furthest ring from the Ark's control terminal and is the last ring to have its hologram light up during the activation sequence
- Like all Halo installations, Installation 07 gets its power from Power Rooms which are connected to others placed around the entire ring.
- The monitor of Installation 07 shares the first three digits of its numerical designation with the service number of John-117, the protagonist of the Halo trilogy and Reclaimer saga. Its numerical designation is also a reference to Bungie's affinity for the number 7 (7^6 = 117649).
- It is speculated that this installation continues to be infested by the Flood, thus its surface should be covered by a slimy, tan-colored biomass they produce on the land (as seen in the Halo: CEA Terminal, 343 Guilty Spark). The yellowish surface of the ring supports this; it is possible that the Flood may have escaped quarantine on this ring.
- Halo 2 (First appearance)
- Halo 3
- Halo Legends
- Halo: Cryptum
- Halo: Primordium
- Halo: Hunters in the Dark