Greater Ark

The greater Ark, also referred to as the Ark, the senescent Ark, or the Beginning Place, was a Forerunner megastructure, and the first of the two Arks used to manufacture Halo rings. It produced the original Halo Array, comprised of rings 30,000 kilometers in diameter as opposed to the 10,000 kilometers of the final Array, which was produced by the smaller Installation 00 instead. Like Installation 00, the greater Ark was located outside the Milky Way galaxy, one-third of the way around the outer boundaries of the galaxy.

Description
Though it shared Installation 00's flower-like shape, consisting of a series of curved arms extending from a circular central section, the greater Ark differed from the lesser Ark in a number of respects; it possessed only six petals, as opposed to the eight arms of Installation 00. Instead of an artificial sun, the greater Ark was illuminated by six shafts of plasma, each suspended over one of the petals, emanating from a tower structure in the center. These plasma tubes would dim and brighten cyclically, approximating a day-night cycle. Each of the greater Ark's arms possessed at least one petal station, from which Forerunner Lifeworkers operated.

The greater Ark possessed a sizable defensive fleet led by the Contender-class Metarch Offensive Bias. By the end of the Forerunner-Flood war, all remaining Forerunner fleets were assimilated into this fleet. After the greater Ark's destruction, Offensive Bias managed to save several thousand warships—only a fraction of its original fleet—and use them to successfully fend off Mendicant Bias in the Battle of the Maginot Sphere.

Commissioning
The greater Ark was commissioned by Master Builder Faber shortly following the end of the human-Forerunner wars in 106,445 BCE, and constructed soon after with the Old Council's approval. Twelve 30,000 kilometer-wide Halos were produced by its Foundry. Over the following millennia, the Builders continued to refine the design of the Halos and soon discovered a number of flaws with the original rings - most notably, their enormous size which made them unwieldy to transport. These plans led to the commissioning of a smaller array of Halos as well as a new Ark to produce them, as the greater Ark was incapable of building smaller installations. However, the construction of the second Ark was delayed by the Council for several thousand years, until the Master Builder gained complete control over it circa 98,445 BCE.

While the greater Ark stopped producing Halos after the original twelve, the installation remained as the most significant repository of the Conservation Measure, the Lifeworker's effort to index and preserve as many sentient species as possible in the event of Halo activation. As a part of the Librarian's pact with the Master Builder, the greater Ark - like its successor - had been constructed to possess a surface capable of supporting various biospheres to house the Lifeworkers' specimens. While the greater Ark served as the primary facility of this enormous undertaking, the lesser Ark remained secret to all but a few in order to ensure it would not fall in the hands of the Flood. At some point in time, the Forerunners placed a holographic projector capable of displaying a Halo from the greater Ark in a repository on Janjur Qom along with a Luminary.

Fall to the Flood
Around 97,445 BCE, strategic command of the ecumene was placed at the greater Ark, as the Capital system was almost completely conquered by the Flood. The greater Ark served as the final refuge for most of the surviving Forerunner population, while the Lifeworkers' specimens formerly stored there were relocated on the nearby Omega Halo, the last surviving ring of the original twelve-strong array (excluding the repurposed Installation 07). The specimens included the Librarian's largest population of humans, which would later be destroyed when the Ur-Didact harvested their essences with the Composer. Shortly after this, the Flood attacked the greater Ark and destroyed it using the Precursors' star roads, leaving the lesser Ark and its new Array of rings as the Forerunners' last resort. The destruction of the greater Ark also led to the death of the majority of the remaining Forerunners, with only a handful escaping to the lesser Ark to carry out their final mission.

List of appearances

 * Halo: Cryptum
 * Halo: Primordium
 * Halo: Silentium
 * Rebirth
 * Halo: Broken Circle
 * Halo Mythos: A Guide to the Story of Halo
 * Halo: Fractures
 * Promises to Keep
 * Halo Wars 2