Installation 08

"A replacement. For the ring you destroyed."

- Thel 'Vadam observing the second Installation 04's construction alongside John-117.

Installation 08 was a partially completed Halo installation which was constructed at the Ark after the destruction of Installation 04. Incomplete to the point where firing would result in its destruction, this replacement was destroyed by Spartan-II Master Chief John-117, only for yet another replacement to be constructed years later.

Background
Installation 08 was designed as a very similar replacement to Installation 04, or Alpha Halo, in order to ensure that the Forerunners' Halo network was intact, and therefore able to encompass the entire Milky Way galaxy.

Construction
Following the Battle of Installation 04 and its subsequent destruction, Installation 00 was notified, and an automated function began building a new replacement for the missing installation's position. The main weapon was built first with the surrounding circular metal structure after by using materials that came from the strip mining moon located at the center of Installation 00.

Before it was released into space, the installation had 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 new installation was also not networked to the other installations, allowing a tactical pulse to be fired without triggering the other six installations. It is never revealed if this is an option available to completed installations as well, although it is likely that the incomplete Installation 08 merely had not been set up with this network yet; a logical precaution considering the effects of a misfire.

At some point prior to the Battle of Installation 00, Cortana became aware of Installation 08's existence. While being held prisoner by the Gravemind on High Charity, she sent a covert message to John-117 on Earth informing him of a "solution to the Flood" that did not require activating the Halo Array.

Discovery
The still-incomplete installation was released into space just above the Ark. John-117 first discovered its existence shortly after he and Thel 'Vadam killed the Prophet of Truth. He decided that the only way to stop the local Flood infestation (which included the Gravemind from Installation 05) was to fire the incomplete Installation, which was out of range of the other rings.

John headed to the Flood-controlled High Charity to retrieve Cortana, as she held the Activation Index from the first Installation 04. Aided in his escape by Thel, John found a crashed Pelican near the exterior of High Charity and piloted it to the incomplete ring. The Pelican crashed in a snowy valley near the ring's Control Room, which was situated atop a high tower. As John and Thel made their way towards the tower, Flood dispersal pods descended from the sky to prevent them from activating the new Halo. The two, aided by Sergeant Major Avery Johnson, fended off the Flood and reunited with 343 Guilty Spark, who let them into the Control Room.

Inside the Control Room, Guilty Spark informed the trio that the installation would be completed in a few more days. However, with Flood reinforcements banging on the Control Room doors, Johnson declared they didn't have time and decided to activate the installation immediately. Guilty Spark, realizing that a premature activation would destroy the new ring, turned against the trio and fatally wounded Sergeant Johnson. The Chief used Johnson's M6 Spartan Laser to seemingly destroy the rampant Monitor. John then proceeded to activate the new Halo with the Index kept by Cortana.

Destruction
"When Halo fired, it shook itself to pieces. Did a number on the Ark"

- Cortana briefing John-117 of the aftermath of their escape.

As Spark predicted, the new installation was not ready to fire, and it began to shake itself apart and disintegrate. John and Thel escaped through the second phase pulse generator chamber and proceeded towards the Dawn in Johnson's Warthog as the shockwave of the activation caused explosive reactions all across the incomplete sections of the installation. John-117 and Thel 'Vadam barely managed to reach the Dawn before the Installation fired and subsequently exploded. Most of the Flood were destroyed in the explosion or perished from the ring's sterilization pulse, including the Gravemind, while the Ark itself suffered severe damage.

By March 2555, a large chunk of the Halo was impaled on the Ark's central hub, like a dead, arcing tree climbing thousands of kilometers into space. There was also debris from the ring in space, some of it still raining down through the atmosphere and blooming into flame before crashing on the Ark's surface. By May 2559, the Ark had completed another replacement.

Despite the ring's activation, a number of Flood forms survived on the Ark as late as October 2559. This may have been due to the variable harmonics of the Halo's pulse and/or because the ring was fired in the midst of its own destruction. The Banished were drawn into a fierce conflict against the Flood on the surface of the Ark. After the Banished killed a Proto-Gravemind and reactivated the Ark's Sentinel defenses, the Sentinels were able to contain the Flood once more.

Replacement of a replacement
During the 's battle with the Banished at the Ark in March 2559, Captain James Cutter, Professor Ellen Anders, and logistics AI Isabel formed a plan to deploy the second replacement for Alpha Halo, Installation 09, to the Soell system in an attempt to send a distress signal to human space. On the way to the original site of Installation 04 however, a Forerunner Guardian construct controlled by Cortana's Created intercepted the ring.

Trivia

 * The multiplayer map Avalanche is located on Installation 08, but Installation 00 and the Milky Way galaxy are missing from the skybox.
 * The Halo Encyclopedia identified Installation 08 (which had not been given an official designation at the time) as Installation 04B. This naming convention has since been retconned by 343 Industries, with the rings' numeric designations being assigned sequentially in their order of construction.
 * The original Installation 04 was destroyed on 22 September and the second one was “just a few days” away from operational capability at the time of its premature firing on 11 December. Given these dates it can be surmised that from conception to firing capability takes approximately three months.

List of appearances

 * Halo 3
 * Halo Legends
 * Origins
 * Halo: Hunters in the Dark
 * Halo Mythos
 * Halo: Official Spartan Field Manual