Installation 04B

"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 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 it 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 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.

At some point prior to the Battle of Installation 00, Cortana became aware of Installation 04B'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 new installation was released into space just above the Ark, but it was still incomplete then. 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-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 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 both the Ark and the new ring, turned against the trio and fatally wounded Sergeant Johnson. The Chief used Johnson's Spartan Laser to destroy the rampant Monitor. John-117 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-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 fired and subsequently exploded. Any Flood not outright destroyed in the explosion perished from the ring's sterilization pulse, while the Ark itself suffered severe damage.

Trivia
The multiplayer map Avalanche is located on Installation 04B, but Installation 00 and the Milky Way galaxy are missing from the skybox.

List of appearances

 * Halo 3
 * Halo Legends
 * Origins