Installation 07

Installation 07, also known as Zeta Halo, is one of the seven rings in the Halo Array. Unlike the other six remaining Halo installations, which were constructed as a separate array of rings with the diameter of 10,000 kilometers, Installation 07 is the only surviving ring from the original main array of twelve 30,000-kilometer-wide Halos. However, the installation's diameter was reduced to 10,000 kilometers after most of its superstructure was discarded as a result of heavy damage.

Forerunner-Flood war
Unlike most of the rings in the final Halo Array, Installation 07 was manufactured at the greater Ark instead of Installation 00 or the "lesser Ark". As a result, it was originally three times the size of a normal Halo ring (30,000 kilometers in diameter). During the Forerunner-Flood war, the ring was placed under control of the AI Mendicant Bias by the Master Builder, who had numerous humans from Earth brought on the ring for study on the effects of the Flood.

Circa 100,043 BCE, the installation was test-fired near Charum Hakkor. As an unprecedented side-effect of this firing, the Primordial, an ancient Gravemind that had been imprisoned on the planet for millennia, was released from its cage and was subsequently taken to the ring for study. Over a period of 43 years, Mendicant Bias interrogated the Primordial, which eventually convinced the AI to go rampant and turn against its masters.

Using the ring, Mendicant Bias attacked the Forerunner capital, but as the installation took heavy damage, it retreated into a distant system through a slipspace portal. Later, the installation was damaged even more when it barely evaded collision with a planet. After being recaptured by the Didact's forces, the ring discarded two-thirds of its mostly damaged structure, contracting to the diameter of 10,000 kilometers in order to allow it to perform a successful slipspace jump to the greater Ark. It was later made one of the rings in the final Halo Array as it was distributed across the galaxy.

Activation
On November 3, 2552, during the Battle of Installation 05, a signal was sent to this Halo from Installation 05, putting the former - as well as the entire array - on standby mode. Installation 07 was then ready to fire on demand.

Deactivation and later history
Later the same year, during the Battle of Installation 00, Installation 00 was still on standby. However, SPARTAN John-117 deactivated the Halo Array before it could be fired, rendering Installation 07 inert.

Through unknown means, the Office of Naval Intelligence later managed to perform a cursory examination of Installation 07, discovering its size and deducing that its surface was overrun by a perpetual cloud cover, although information on the ring remained sparse. The cloud-covered surface led an ONI scientist to speculate on whether the ring's life support systems had never recovered from the damage it sustained 100,000 years prior.

Trivia
The installation surface resembles Venus' surface.

List of appearances

 * Halo 2 (Holographic representation)
 * Halo 3 (Holographic representation)
 * Halo: Legends
 * Origins
 * Halo: Combat Evolved Anniversary (Terminals only)
 * The Forerunner Saga
 * Halo: Cryptum
 * Halo: Primordium