Installation 08

"A replacement, for the ring you destroyed."

- The Arbiter observing the second Installation 04's construction alongside John-117.

The Replacement for Installation 04 was a partially constructed Halo Ring which was started at the Ark after the destruction of the original Installation 04.

Background
This Installation was designed as a near identical replacement to the previous Installation 04. This was to ensure that the Forerunner's Halo Network was intact, and therefore able to encompass the entire Milky Way galaxy.

Replacement
Immediately after the Battle of Installation 04 and the destruction of Installation 04, The Ark was notified, and some automatic function started building a replacement for the missing Installation's position. The main weapon was built first with the surrounding circular metal structure after it. It is unclear how the Ark was able to create the new installation or what the source of raw materials for its construction was, as no insight is given to those functions of Installation 00. Before it was released into space (presumably work was to finish there before being sent to Threshold to replace the original Installation 04 destroyed at the end of Halo: Combat Evolved) the Installation has a number of primary features available even though it was still not complete, these included the environment, atmosphere and main structures and the main weapon, though the ring structure was not yet stable enough to survive this weapon's discharge. The ring was also not connected to the other Installations, allowing a tactical pulse to be fired without triggering the other 6 Installations. It is never revealed if this is an option available to completed installations as well.

Destruction
The new Installation was released into space just above the Ark, but was still incomplete. The Master Chief and the Arbiter decided that the only way to stop the local Flood contamination (which included the Gravemind from Installation 05) was to fire the incomplete Installation, which was out of range of the other Halo rings.

The Chief heads to the Flood-controlled High Charity to retrieve Cortana, as she has the Activation Index from the first Installation 04.

After retrieving Cortana, during his flight from High Charity, the Chief destroys the main reactor core (at Cortana's suggestion). This damages, but does not destroy, the Gravemind. Aided in his escape by the Arbiter, the Chief finds a crashed Pelican on the exterior of High Charity and pilots it to the Control Room.

The Pelican crashes in a snowy valley near the Control Room, which is situated atop a high tower (as in Installation 04's). As the Chief and Arbiter make their way towards the tower, Flood dispersal pods descend from the sky, and the Gravemind reveals that he is not yet defeated.

After battling to the top of the tower, aided by Sergeant Major Avery Johnson and his Spartan Laser, the team reunites with 343 Guilty Spark.

Final Moments
As they enter the Control Room, Spark states that the Installation will be ready to fire in "just a few more days", and that a premature firing would destroy the ring, and the Ark with it. However due to the gravity of the situation, Johnson replied curtly that they don't have "a few more days", and attempts to unite Cortana with the Control Core.

This is too much for 343 Guilty Spark, who regards the installation as his. He enters full Rampancy, (or he could have just been carrying out his original programming, which would have been to ensure the safety of any Installation) and fires on Johnson with his Sentinel Beam, mortally wounding him.

The Chief rushes to Johnson's aid, and is knocked down by Spark's beam, which is then turned on the Arbiter, who is knocked out of the door, which closes. Johnson fires his Spartan Laser on Spark, before lapsing into unconsciousness, this stuns Spark. Johnson gives the Laser to the Chief with the words "Kick his ass". After three shots from the Laser, Spark explodes and the Chief is finally able to unite Cortana and the Core.

As Spark predicted, the ring was not ready to fire, and it begins to shake itself apart and disintegrate. Master Chief and the Arbiter escape through the first Phase Pulse Generator room, and then to Johnson's Warthog. The vibration of the activation begins to tear the Installation apart, causing explosive reactions all across incomplete sections of the installation. Master Chief and the Arbiter barely managed to reach the UNSC Frigate, Forward Unto Dawn, before the ring detonates. Cortana states that the ring's explosion "did a number on The Ark."

Trivia

 * In the Control Room the hologram of Threshold is missing and if the control room is viewed from above it looks like an entirely black circle. If Threshold was present it would have a blue centre, this draws paralell to a glyph during the Iris campaign, which was missing the circle in its centre compared to all the others.
 * Judging the time taken from the original Installation 04 destruction (September 2552) and the appearance of the new Installation 04 (March 2553) it appears that to get a full working Installation weapon, partial environment and structures only takes around 6 months, but since Installation 04 (II) was not finalized (environment, structural stability etc) it could take an extra 6 months to be finished. So in total to replace one Installation at one time it could take up to one Earth year. (This is also not counting how long it would take to get back into the previous Installations position, or even how it would get there.)