Anodyne Spirit

Forerunner Dreadnought "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

The Forerunner Dreadnought, also known as the Key ship and colloquially known as the Forerunner Ship, was a Forerunner warship classification used in the Forerunner-Flood War.

They were also large part of the Forerunner strategy against the Flood, as they were the only vessels capable of activating the Portal to reach the Ark. One of these dreadnaughts would miraculously survive the Forerunner-Flood War and would become an integral part of the Covenant religion.

Specifications
The Forerunner Dreadnought is a geometric and angular warship, sharing many aesthetic features with other Forerunner constructs. Generally, it has 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, its hull its grey or silver in color, and it is 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. The Dreadnoughts were an integral part of the Forerunner-Flood War, and were used as warships in confrontations such as the Battle of the Maginot Sphere, and were also used to travel through Portals to the Ark. Although their weapons systems were unknown, one Dreadnaught was found and used by the San 'Shyuum during the Sangheili-San 'Shyuum War, and was far superior to Sangheili vessels of the time. During the Human-Covenant War, the same Dreadnoughts were resistant to even the heaviest of UNSC ship borne armaments, specifically the Magnetic Accelerator Cannon systems. The Forerunner Dreadnaught has been known to carry over 1,000 people, which is believed to be only a fraction of its true carrying capability.

History
The history of the Forerunner Dreadnaught is quite extensive, going back about 100,000 years.

Forerunner-Flood War
The Dreadnought was used extensively by the Forerunners in their war against the Flood. A number of Dreadnoughts were given to the Librarian, and combined with her ability to build Portals, the Librarian was able to transport herself back to the Ark with her Dreadnoughts if the situation required. The Librarian, however, bravely destroyed her Dreadnoughts 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 Dreadnoughts 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 Didact was in command of multiple Dreadnoughts, although near the end, when the Forerunners began generating Slipspace ruptures to destabilize the battlefield and destroy Flood craft, Dreadnoughts were recklessly piloted near the rifts, destroying them. However, at least one Dreadnought would survive the war and be rediscovered.

Rediscovery
Main Article: San 'Shyuum Civil War

Early in the history of the San 'Shyuum, they found and worshipped the Forerunner Dreadnought. These early worshipers were split over the usage of the ship, as the Stoics refused to enter the vessel, while the radical Reformists wished to explore it. The Reformists then barricaded themselves within the dreadnaught, and left the San ‘Shyuumn home world, taking a piece of the planet with them.

Sangheili - San 'Shyuum War
Main Article: Sangheili-San 'Shyuum War

After leaving their home world, the San 'Shyuum encountered the Sangheili, who also had familiarity with Forerunner technology. The San 'Shyuum believed that incorporating Forerunner technology was allowed by their religion. To the Sangheili, such a thing would have been unthinkable.

During the combat, the Sangheili had an early advantage, with each warrior comparable in skill to several San 'Shyuum in battle. However, the San 'Shyuum's technological superiority, and possession of the Forerunner Dreadnought, meant that they had the advantage in space, using the Dreadnought to great effect in devastating hit-and-run strikes against the Sangheilian Fleets. Eventually, the Sangheili were forced to amend their position of the treatment of Forerunner technologies and began incorporating elements into their designs.

Eventually, in order to ensure the survival of both races, the two races merged to form the early Covenant with the San 'Shyuum as the head religious leaders and the Sangheili as the physical backbone.

Writ of Union
The two races then penned the Writ of Union, which formally began the Covenant, and decommissioned the Forerunner warship, removing all known weapons, and placing it within the partially completed High Charity. It was then used to power the city, with its engines at partial power.

The Great War
Main Article: Human-Covenant War

Before the start of the Human-Covenant War, the Forerunner Dreadnaught, the founding of the Prophet’s religion, would soon become the place where their religion was proven false. During the 23rd Age of Doubt, the Minister of Fortitude, and the Vice Minister of Tranquility went to the Forerunner Dreadnaught for confirmation of two symbols found on the missionary vessel Minor Transgression. These two symbols were “Reclamation” and “Oracle”, which were found on what was known to Humanity as Harvest. After activating the Oracle inside of the Dreadnaught, it began a series of cryptic messages, listed below:

FOR EONS I HAVE WATCHED LISTENED TO YOU MISINTERPRET THIS IS NOT RECLAMATION THIS IS RECLAIMER AND THOSE IT REPRESENTS ARE MY MAKERS I WILL REJECT MY BIAS AND MAKE AMENDS MY MAKERS ARE MY MASTERS I WILL BRING THEM SAFELY TO THE ARK

During this series of messages, the Oracle began a launch sequence, which would rip the Dreadnaught from High Charity and destroy the artificial planet with it. The oracle was disconnected, but this caused a spiritual crisis for Fortitude, Tranquility and the Philologist. Through the Oracle’s messages, the Forerunners (or their descendants), were still alive, which would shake the foundations of the Covenant itself to the core. In an attempt to keep the religion itself intact, they covered up the encounter, and would try and eradicate these Reclaimers.

For most of the Human-Covenant War, the Dreadnaught remained a purely religious artifact, not a weapon, until the Battle of High Charity.

The Battle of High Charity
When the Flood attacked High Charity, SPARTAN-117 was on his way to stop the Prophet of Truth from escaping and at the end of the Battle of Installation 05. He was able to board the ship as Truth uncoupled it from the city's power grid by narrowly making it through a conduit and into the opening it connected to. The Forerunner Dreadnaught lifted off, and slipspace jumped in the midst of a large three way battle between Covenant Loyalists, Covenant Separatists and the Flood. It’s destination was unknown until the Forerunner Dreadnaught exited slipspace around Earth.

Second Battle of 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 Forerunner Ship itself would soon become a battle ground as Master Chief tries to assassinate Truth.

Onboard the ship, Master Chief was contacted by a station on Io, but after going into radio silence, he killed four grunts, a pair of Jackals and then another group of four grunts. It is unknown what happened immediately afterward, but soon, Master Chief was found unconscious by a group of Brutes. The Brutes interrogate him, asking him where the Key of Osanalan is, when S-117 replies: “It means… always strip your enemy of weapons before you interrogate him”. The Brute looks down to see a plasma grenade, which soon detonates, killing him, a few other brutes and scattering the confused Unngoy. After making his way to the Prophet of Truth’s position, he reports to the UNSC that one Prophet Hierarch is onboard and will transmit more information later. Then, Spartan-117 takes aim at Truth with a Covenant Carbine and fires.

Sometime afterward, Spartan-117 jumped from the Forerunner Dreadnought as it descended to Earth, falling two kilometers into the African jungle. The Forerunner Dreadnought continued its descent and landed on the portal to the Ark.

Though it is never explicitly stated, the Forerunner Ship is most likely 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 its "true resting place" during game play.

The remaining UNSC forces on Africa planned to launch a surprise strike on the Dreadnought to eliminate Truth and stop it from activating the structure they thought to be The Ark. The Master Chief led a Marine assault on a Covenant loyalist anti-air battery sector in the town of Voi and successfully disabled the battery, giving the UNSC a clear shot at the Dreadnought. Lord Hood then attacked the ship with a squadron of Longsword fighters and three UNSC Frigates. The Dreadnought's advanced Forerunner armor allowed it to survive three MAC rounds and several missiles, and the UNSC attack was halted when the Portal was activated by the Key Ship.

After activating the portal, the Dreadnought entered it and landed on The Ark. It did not take part in the battle. The ship was possibly damaged beyond use from the combined effect of slipspace transition and the attack, and was most likely destroyed when the Halo destroyed itself.

Trivia

 * 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 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 existence at the time the Halo incidents take place as it’s able to power all of High Charity, even when not at full generating capacity.