Keyship

"I've remotely destroyed our Keyships. A security measure. Without them I cannot reach the Ark. But neither then can the thing."

- Librarian to the Didact.

Keyship is a classification of supra-luminal Forerunner vessel in use at the time of the Forerunner-Flood War. Keyships were capable of activating slipspace portals leading to the Ark. Though many more once existed, the majority were destroyed by the Librarian to prevent the Flood from reaching the Ark.

The Forerunner Dreadnought, as it was known by the Covenant, was a Keyship.

Specifications
Keyships are geometric and angular, sharing many aesthetic features with other Forerunner constructs. Generally, they have a tetrahedral shape, with a forward triangular prow, and attached to it at equidistant points are three similarly shaped struts, to help ground the ship. Visually, their hulls gray or silver in color, and was estimated to be about 14 kilometers (8.699 miles) tall, 37,654 tons in weight, far heavier than leisure craft, but outweighed by a variety of transport and military vessels.

Although their weapons systems are unknown, one Keyship was found and used by the San 'Shyuum during the Sangheili-San 'Shyuum War, and was far superior to Sangheili vessels of the time. At the time of the Human-Covenant War, the same Keyship's shielding was completely impervious to even the heaviest of UNSC shipborne armaments, specifically the Magnetic Accelerator Cannon systems. A Keyship has been known to carry over 1,000 beings, which is believed to be only a fraction of its full carrying capacity. They were capable of remote detonation to prevent their usage by the Flood.

A Keyship consists of thousands of rooms, many of which are docking bays and control rooms, including a command chamber which was many stories high.

Forerunner-Flood War
During the Forerunner-Flood War, there was an entire fleet of Keyships, used extensively by the Forerunners in their war against the Flood. A number of Keyships were given to the Librarian, and combined with her ability to build Portals to the Ark, the Librarian was able to transport herself back to the Ark with her Keyships if the situation required. The Librarian, however, destroyed her Keyships to prevent them from falling into the hands of the Flood, who with them, would be able to instantaneously travel to the Ark, rendering the Halo Array useless.

Near the end of the war, the Keyships were part of an unknown strategy to hold off the Flood for nearly 79 years, although this advantage would be foiled by the massive computing power of the Flood. At the Battle of the Maginot Sphere, the rogue AI Mendicant Bias commanded at least one Keyship, which managed to escape and eventually find its way to the San 'Shyuum homeworld.



Key to repopulation
Keyships were also an integral part of the Forerunners' Library Project to preserve sentient life. Before the firing of the Array, the Forerunners gathered DNA and living specimens of the notable sentient species located throughout the galaxy and protected them from the devastation of the Flood and all other life via Halo by transporting them to the Ark. After the seven ringworlds fired out their pulses, several Keyships, containing preserved specimens of each species, were sent to the planets from which the sentient species originated, and released a population of the species on their planet of origin. These ships therefore were not only a vessel of war, but also designed to reinstate life on the planets devastated by Halo.

Legacy
Mendicant Bias would find his way onboard a Keyship to the San 'Shyuum homeworld. By 2552, that particular vessel, referred to by the Covenant as the Forerunner Dreadnought, was most probably one of, if not the last surviving Forerunner Keyship in existence, used by the Covenant for an unknown amount of time as an unusual source of power for their holy city, High Charity. At the end of the Ninth Age of Reclamation, the Prophet of Truth appropriated the dreadnought to activate the Portal on Earth and travel to Installation 00. It was last known to have gone to ground on said Installation, and is believed to have been destroyed upon the premature activation of Installation 04B.

List of appearances

 * Halo: Combat Evolved Anniversary
 * Halo 2
 * Halo 3
 * Halo: Contact Harvest
 * Halo Legends
 * Origins