Installation 08

Were you looking for the original Installation 04?

"A replacement. For the ring you destroyed."

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

Installation 04B was a partially completed Halo installation which was under construction at the Ark since the destruction of the original Installation 04.

Background
This Installation was designed as a very similar replacement to the original Installation 04 in order to ensure that the Forerunner's Halo Network was intact, and therefore able to encompass the entire Milky Way galaxy.

Creation
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 it using materials came from the Ark's Core, a planetoid 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 Installation 04B merely had not been set up with this network yet, as it was incomplete; a logical precaution considering the effects of a misfire.

Discovery
The new Installation was released into space just above the Ark, but it was still incomplete then. John-117 and Thel 'Vadam 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-117 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 Control Room. The Pelican crashed in a snowy valley near the 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 the two from activating the new Halo. The two, aided by Sergeant Major Avery Johnson, reunited with 343 Guilty Spark. When the Sgt. Maj. Johnson tried to force-fire the new Installation, the Forerunner Monitor interrupted the process because of protocols and possible hints of rampancy, and engaged the three. With 343 Guilty Spark eliminated, John-117 activated 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-117 and Thel 'Vadam escaped through the second Phase Pulse Generator chamber and proceed towards the Dawn using Sgt. Maj. Johnson's Warthog. The shockwave of the activation began to tear the Installation apart, causing explosive reactions all across incomplete sections of the installation. John-117 and Thel 'Vadam barely managed to reach the Dawn before the Installation exploded.

Trivia

 * The multiplayer map is located on Installation 04B, but the Installation 00 and the Milky Way galaxy are missing from the skybox.
 * It seems that key places like the Control Room and the Silent Cartographer would be on the finished parts of the ring, as the Control Room had at least a mile of complete, sound structure around it.
 * The near-completed Installation shows the prowess of the Forerunners' stellar engineering as it was built completely from scratch in a matter of months.
 * The Control Room tower resembles the tower seen on Installation 04, but the corridors on the inside are more like those seen on Installation 05; the directions turned are the same, while in Halo: Combat Evolved, it was almost straight. The Control Room itself is the same as the original Control Room of Installation 04. It is likely that this was an oversight, or it could show that the design of the Halo rings is constantly updated.