Containment shield

For the barrier that once surrounded the San'Shyuum home system, see quarantine shield. Containment shields are massive hard light barriers that can be created by Sentinel forces to quarantine an area. One was projected from the Sentinel Wall around Installation 05's Library. One of the many containment measures built by the Forerunners, it helped contain and enclose the Flood inside the Quarantine Zone, and keep out anything that could sustain the Flood. It had to be lowered and deactivated in order to enter the Library and recover the Activation Index.

Installation 05
During the Battle of Installation 05, the containment shield kept UNSC and Covenant forces stationed on Delta Halo from reaching the Index. In order to gain access to the Library and retrieve the Index, the Hierarchs of the Covenant dispatched Arbiter Thel 'Vadamee to lower the shield. The Arbiter fought his way through the Sentinel defenders to the enormous chamber containing the controls for the barrier. After destroying the Sentinel Enforcer guarding the chamber, the Arbiter retracted four piston-like plug locks which unlocked the main control panel, allowing him to lower the shield. This caused the entire two-tiered control platform to move to the other side of a large chasm in the middle of the Sentinel Wall in a manner similar to an anti-gravity gondola.

The deactivation of the shield allowed access to the Quarantine Zone by the Covenant and the UNSC, which also gave the Flood hundreds of new hosts. The Flood was released onto the rest of Installation 05. As a result of this, the was taken over by the Flood and flown into the Covenant city of High Charity.

Installation 00
Three days after the Human-Covenant War ended, Sentinels set up a containment shield around the ruins of High Charity that survived the detonation of its backup reactors and Installation 08's firing and subsequent destruction.

During the Second Ark Conflict in 2559, Voridus, a Jiralhanae commander of the Banished, destroyed a part of the containment shield with a Scarab, leading to a second Flood outbreak on the Ark. This in turn caused Atriox to abandon his plans to destroy the humans on the Ark for the time being in order to stop the Flood threat. Afterward, the containment shield remains around the ruins of High Charity, despite Voridus shutting down the Sentinel defense network. After Voridus and Pavium defeated the Proto-Gravemind that had emerged and reactivated the network, swarms of Aggressor Sentinels headed towards High Charity to resume the containment operation.

Trivia

 * In Halo 2, the containment shield was observed during the level Sacred Icon.
 * The holographic control panel for the shield displays what appears to be a perfectly symmetrical hand with six fingers. Whether by coincidence or not, this matches the later depictions of Forerunner hands in Halo 4 and The Forerunner Saga, which establish most Forerunners as having six-fingered hands with two thumbs.

List of appearances

 * Halo 2
 * Halo 2: Anniversary
 * Halo Wars 2