Sanctum of the Hierarchs

The Sanctum of the Hierarchs is the name given to the private quarters of the High Prophets on High Charity. They are restricted to virtually all other creatures, except the Honor Guard, San 'Shyuum and Sangheili Councilors and high ranking Covenant officers, such as Special Operations Commanders and Arbiters.

Description
The Sanctum consisted of many rooms, including the Inner Sanctum as well as a massive room decorated with shards of glass from the countless worlds devastated by the Covenant. The Inner Sanctum featured unique architecture, highly ornamented doors and various other luxuries. The Sanctum has several entrances; one is via a lift in the Council Chamber, and another is a large hallway where dozens of Honor Guards used to stand watch. The higher levels of the Sanctum, or the Far Tower, also include three tenders for Phantom dropships. The center of the inner room also featured a Holotank which also had another mechanisms, such as serving as a stasis field emitter.

The Sanctum contained another room, a massive chamber with its walls, floor, and ceiling ornamented with smooth glass from all the worlds conquered by the Covenant. This chamber was a large, round room with an illuminated pedestal in the center. On the perimeter of the room, there was space for three hundred Honor Guard Elites, should a Prophet be present.

History
After Operation: FIRST STRIKE, the High Prophet of Truth and Tartarus, Chieftain of the Brutes discussed the events that took place on Installation 04, as well as the fate of the future Arbiter, the pilots, and the destruction of the Unyielding Hierophant, in the Sanctum.

Many events took place here, including the Changing of the Guard when the Jiralhanae supplanted the Sangheili as the Honor Guards and minders of the Prophets, after the assassination of the Prophet of Regret. It was here that the Prophet of Truth and the Prophet of Mercy explained to the Arbiter his task of landing on the surface of Installation 05 and retrieving the Index from the Flood infested Library, which took place in two levels through the Sentinel Wall and the Quarantine Zone.

In the end, the Flood used Pelican dropships to land in the Sanctum. It was one of the first areas to be infested; it was filled with Spores and Flood "structures" when the Master Chief traversed the area in search of the High Prophet of Truth.

When John-117 returned to High Charity in order to rescue Cortana, she was being held inside a stasis field in the holo-pad in the center of the Sanctum. The room was connected to the reactor room that was not accessible in Halo 2 due to a series of locked doors. The room had been dramatically altered by the Flood infestation: there were widespread structural failures that occurred as a result of High Charity colliding with the surface of Installation 00.

Trivia

 * In Halo 2 when you enter the room, you can see a dead Elite Minor with an Energy Sword on the nearby obelisk and another on a pronged pedestal.
 * During the Sacred Icon cutscene, 343 Guilty Spark can be seen floating in the holotank. Whether he is floating on his own or a stasis field is holding him is unknown.