Halo Alpha
Halo Alpha

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Not to be confused with the Installation 00, also known as the Lesser Ark.

The Greater Ark was an enigmatic Forerunner installation from which all the Halo installations across the galaxy can be activated simultaneously. In addition, it functioned as a safe haven from the Halo network's strategic pulse, as well as a facility to construct and repair any of the original installations of the Halo Array. Like Installation 00, the Greater Ark was located beyond the galactic rim, but this Ark's location was more widely known.


The Greater Ark was part of the Master Builders plan for battling the Flood, this plan consisted of the twelve original Halo rings, and a smaller Ark, Installation 00. Located about 260,000 light-years from the galactic center, the Greater Ark was located outside the galaxy and was thus safe from the Halo Array. The purpose of this installation was to remotely activate the 12 original Halo rings then in existence, from outside the blast radius of the array. In addition, this installation can also function as an automated factory to construct replacement Halo installations (but only the original 30,000 km ones).

This installation was the The Librarian's original haven for her species, but they had to be moved when more Forerunners moved to this location, due to Flood expansion.

One of the last battles in the Forerunner-Flood war took place in the space around this installation. In this battle, the Flood used captured Forerunner ships, and star roads to engulf the Ark, and soon after destroy it. The only survivors of this battle were the Ur-Didact, the IsoDidact, the Librarian, a small Forerunner fleet (this fleet may not have come from this battle though) and a number of Lifeworkers.

It was in orbit around this Ark where the Ur-Didact composed the human populations on the Omega Halo.  The Omega Halo was destroyed during the battle, killing everyone on it (including the Master Builder). The only known survivors from the destruction of the Omega Ring and the Greater Ark were the Librarian, the Ur and Iso Didacts, and 343 Guilty Spark (Who took with him a Gargantua class ship with some of the Librarian's human specimens on board).

Layout and Function[]

The Greater Ark was of a similar shape to Installation 00, but with only six "petals" protruding from the center of the structure and on a larger scale. Like the Lesser Ark, the Greater Ark has the ability to remake or fix Halos, but can only do this for the larger, weaker original Halos.