Anodyne Spirit

History
The Forerunner Dreadnought, also known as the Key Ship, was built by the Forerunner and was part of their plan to activate the Halos. The ship itself has a design characteristic of all Forerunner constructs; it is very geometric and angular with no apparent rounded surfaces. It is estimated to be about 14 kilometers (8.694 Miles) tall, travels vertically like a rocket and can enter Slipspace. . Early in they're history the Dreadnought was found and worshipped by the San 'Shyuum. These early worshipers were split over the usage of the ship, as some thought it should only be viewed while others thought they should try and learn as much as possible from it, the latter side won out and managed to use the ship to escape, although it was only partially operational. It was used in the later San 'Shyuum/Sangheili War where it was able to decimate the Sangheili warships in devestating hit-and-run attacks, until the Sangheili began learning from Forerunner artifacts to improve they're own ships. This then brought the war to a virtual standstill and a peace was finally established.

They then wrote the Writ of Union, which formally began the Covenant, and decommissioned the Forerunner warship, removing all known weapons, and placing it within(at the time) the partially completed High Charity and then used to power the city. .

At the begining of the Ninth Age of Reclamation the ship's A.I. was given data that concerned the location of a Human world, Harvest. This in turn caused it to start a launch sequence to travel to the planet. It was only stopped when Lekgolo worms were able to short the control systems and then soon after the A.I. itself was isolated from the rest of the ship. Had the ship launched, it possibly could have killed every living being in the city as the atmosphere would have vented into space.

Storyline
When the Flood attacked the city, SPARTAN-117 was on his way to stop the Prophet of Truth from escaping and at the end of Halo 2, he was able to board the ship as Truth uncoupled it from the city's power grid (presumably, it was the Prophet of Truth that was using it since High Charity was overrun by the Flood and he couldn't use that safely to get to Earth). It then left the system with the Halo and headed for Earth.

Soon after it arrived in orbit around Earth, Lord Terrence Hood was about to give the order to destroy it. He only stopped because he found out that the Master Chief was aboard.

The Dreadnought then landed in Africa, a continent on Earth.

The ship landed in the center on what would come to be known as the portal to the Ark. It is probable that the Forerunner Ship is an undestroyed Key Ship, which would activate the Ark portal. This is evidenced by its apparent activation of the Ark portal on Earth while it was landing in the middle, and Truth calling the Ark portal on Earth it's "true resting place" during gameplay dialogue. However, while its presence there during activation may be mere coincidence, the fact that it was used to directly channel Ark portal energy makes this unlikely. After the portal activation, the Dreadnought left with all of Truth's ships through the portal. At this point it is not seen again and it is unknown what happened to it. It is likely, however, it may have survived because of how resilient it was, the evidence being that immediately before the Ark Portal activation, the ship itself was attacked by Lord Hood's ships and took several direct MAC Cannon hits without sustaining any apparent damage. It probably had landed on the Ark as it did not take part in the battle above the installation.

Trivia
The ship itself has given the Covenant much knowledge, an example being how to construct a Luminary.

It is known there is a Forerunner A.I. in the ship, although at the very beginning of the 9th Age it was isolated from the rest of the ship. However, the Covenant may have installed they're own, the evidence being the presence Cortana found while trying to slow its launch sequence.

According to the account by Forerunner AI Offensive Bias in the sixth Terminal, he controlled dreadnoughts exactly 37,654 tonnes each, in his battle with the Forerunner AI Mendicant Bias. This may be the same class of ship although it is likely it was a special class of Dreadnought designated the Key Ships.

"Dreadnought" may be just a classification for the ship and it might be the Sharquoi mentioned in Conversations from the Universe.

The Dreadnought is thought to be the fastest ship in existance at the time the Halo incidents take place as its able to power all of High Charity even when not at full generating capacity.