Guardian Custode

"031 Exuberant Witness"

Guardian Custodes, commonly known simply as Guardians, are powerful Forerunner constructs built to enforce the Mantle within the ecumene. Custodes are part of a wider category of policing constructs known as Peacemakers. Along with the Preceptors, the Guardians were classified as tier-two Peacemakers that were largely used to enforce order among the Forerunners' lesser subject species rather than Forerunner-inhabited systems.

Manufactured by the Minoris Assembler Vats, the Guardians were controlled by ancilla and operated through their connection to the Domain. In October 2558, Cortana took control of the Guardians to enforce the will of her Created.

Design and operation
"Whoa. They built them big, didn't they? Figure that's the Guardian?"

- Spartan Edward Buck, upon first spotting a Guardian

The body of the Guardian Custode is variable and ever-changing, shaping itself to awe, inspire, and maximize effectiveness of all defensive systems. Generally, Guardians have a segmented body and elaborate, phoenix-like wings consisting of multiple segments. They possess a head that is vertically roughly elliptical, topped with a broad, vaguely conical protrusion and a roughly humanoid face similar to that of the Promethean constructs. The appearance of the Guardians unnerved many Forerunners, though all attempts to change their look were unsuccessful. The Guardians are enormous constructs, measuring just over 1,412 meters (4,635 feet) in height, with a mass of two hundred million metric tons.

They are capable of concealing themselves underground, underwater, and under lava, and are also capable of traveling through slipstream space. The wings of the Guardians, known as "focus wings", contain energy condensers which draw power from the surrounding quantum vacuum. They also contain effectors which magnify the Custode's electromagnetic pulse. Guardian shielding is capable of withstanding the attack from a human frigate's Magnetic Accelerator Cannon, as well as numerous missiles. Guardians had the authority to plant assembler vats on the worlds they monitored, which would eventually grow and expand to staging areas and factories for the lesser Sentinels and weapon-ships that served them.

The constructs have no crew and instead each Guardian is controlled by an ancilla who inhabits the Custode. These ancillas have limited personality and empathy, having grown strange and aloof. Service as a Guardian and deep synchronization with the Domain reshaped the minds of the ancillas into a form that was considered best suited to serve the Mantle of Responsibility and enforce the prime directives that had first been outlined when even the Forerunners were young. Guardians were connected to the Domain's overwatch network, which allowed them to reflexively counter many threats to the ecumene long before they gained the attention of Warrior-Servant commanders.

Guardians were closely attuned to the ecumene's legal authorities, with the Domain ensuring that the constructs were often available to assist or monitor their activities. Through their connection to the Domain, the Guardians recorded the feats and struggles of those under their protection into the archives of the Domain. Occasionally, Guardians would take independent action to serve a greater purpose when the Domain resonated with these events.

Armaments
"Guardian's got a hell of a singing voice."

- Edward Buck, as a Guardian prepares to fire its disruption generator

The Guardian Custode's primary weapon is a single disruption generator, a devastating weapon capable of destroying infrastructure caught in its blast. The Guardian is equipped with two attenuation pulse emitters—a multi-vector electronic warfare weapon that can instantaneously neutralize local power networks through a series of debilitating pulses, capable of even disabling Forerunner systems.

Guardians are also armed with six converging beam cannon emitters, weapons commonly found on Forerunner warships that emit tendrils of energy that track enemy vessels and create a path for antimatter streams to pursue. While six of these beam cannons were more than adequate to defeat the fleets of primitive capital ships, they were of little use when the Guardians faced Forerunner warships infested and captured by the Flood.

Roles
"Jameson Locke"

The Guardians were classified as tier-two Peacemakers, specifically purposed for security, protection, and enforcement roles within the ecumene. However, the Guardian Custodes were first used as tenders and recorders of the Precursor legacy, though this purpose has long since faded out of living memory. While efficient protectors and enforcers, Guardians also served as immaculate record keepers, adding the history of those under their protection to the Domain's archives.

The Mantle of Responsibility, the philosophical system adhered to by the Forerunners, was based around the belief that the most technologically developed species was charged with the stewardship of life throughout the Milky Way galaxy. As such, the Forerunners considered themselves the Mantle's upholders. However, as part of the Mantle's "code", competition and conflict was allowed as long as it did not threaten galactic biodiversity. As such entities proved to be a threat to the Forerunners' hold of the Mantle, the Guardians were designed to police the so-called "lesser" planetary systems and enforce the Mantle's edicts on non-compliant or overly aggressive species. Guardians were utilized throughout Forerunner history to suppress rebellions or were deployed in advance as an imposing threat of force. However, they ultimately proved useless against the parasitic Flood.

Guardians were designed with multiple roles and functions, though their primary purpose was the monitoring and subjugation of all local power networks on subject worlds. If deemed necessary, Guardians could instantaneously neutralize these power networks through a series of debilitating pulses that incrementally increased in power. A single Guardian was often enough to effectively police an entire planetary system, though the deployment of multiple Guardians at one location allowed the constructs to strategically coordinate their strike, rendering all but the most sophisticated foes completely ineffective. This method of control was largely unchallenged by other species in the galaxy.

Tools of the Mantle
The Guardians were developed and created by the Forerunners to enforce the Mantle of Responsibility by keeping "lesser" systems in line. The constructs were first deployed many millennia prior to the Forerunner-Flood war, created by the Forerunners before the time of the ecumene as tenders and recorders of the Precursor's legacy. However, this purpose has long since passed out of living memory.

Throughout Forerunner history, Guardians quelled rebellions and neutralized threats. During the Forerunners' war with the Flood, Guardians were used in an attempt to combat the Flood but proved useless against the biological parasite. While the Guardians' weapons proved devastating against the fleets of "lesser" species, they were no match against the Forerunner warships captured by the Flood. As the Flood brought on the fall of the ecumene and the near-extinction of the Forerunners themselves, the Forerunners buried the remaining Guardians on isolated shelter worlds. With the firing of the Halo Array in 97,445 BCE, the Guardians were left behind when the remaining Forerunners left the galaxy; the constructs would remain dormant on their shelter worlds until called upon to serve the Mantle once again.

The Guardian located on Sanghelios beneath the Csurdon Sea would later be found by the native Sangheili dive-hunters and fishing skiffs before the species even became space-faring. Nearby elders built fortresses to observe and protect the Guardian's location, which they deemed sacred. The city of Sunaion was later built over the Guardian's location in the sea as a temple to worship the construct and its creators. The Covenant later explored the Guardian for many years in an effort to learn of the construct's nature, but their attempts proved fruitless.

At some point after the shield world of Sarcophagus was colonised, the Office of Naval Intelligence set up Project GOLIATH to study the Custodes, with Lucy-B091 having some level of involvement with the project.

Reemergence
"She calls the Guardians to serve her!"

- The Warden Eternal, referring to Cortana

In 2558, Cortana, who had been restored within the Domain and come to believe that the Created — human artificial intelligences — were the true inheritors of the Mantle of Responsibility, intended to use the Guardians to enforce the Mantle among all the galaxy's species. She thus began to activate the Guardians across the galaxy and summon them to the nexus of her power at Genesis. Sometime after Dr. Catherine Halsey was rescued from Onyx, she discovered a signal that was being bounced around several locations across the known galaxy. One of the sources of the signal caused violent seismic activity on an unknown human colony, leaving only the symbol of the Guardians. Later, in 2558, Halsey helped the Office of Naval Intelligence access her data archive, leading to ONI hiding the presence of the Guardians from humanity.

In October later that year, Guardians emerged on at least twelve human colonies, including Meridian, Conrad's Point, Ursa IV, and Laika III, as well as other worlds inhabited by species of the former Covenant. These colonies suffered greatly from the devastation caused by the constructs' activation. When Blue Team boarded a Guardian on Meridian, the UNSC held Blue Team's leader, John-117, responsible for the attacks. Fireteam Osiris, led by Jameson Locke, was assigned to hunt him down. Later, Fireteam Osiris was tasked with retrieving a Constructor in a Forerunner structure on Sanghelios in order to activate a Guardian that had been buried under the nearby Csurdon Sea. Soon, all of the Guardians that had been awoken would soon be called to Genesis, and then be dispersed throughout human space, to serve the reclaimed Mantle of Responsibility once again.

In early April of 2559, a Guardian intercepted and captured Installation 09 en route to the Soell system from Installation 00. On the surface of the Halo the Guardian confronted Professor Ellen Anders, who had gained control of the ring during the crew's war against the Banished on the Ark.

Known Guardians
This is a list of all notable Guardians.
 * Cortana's Guardian: Cortana unsuccessfully attempted to store Blue Team's Cryptum inside this Guardian.
 * Conrad's Point Guardian
 * Ursa IV Guardian
 * Laika III Guardian
 * Oban Guardian: This Guardian took an unsuspecting UNSC Marine who was on patrol to Genesis.
 * Meridian Guardian: The Guardian that took Blue Team to Genesis.
 * Sanghelios Guardian: The Guardian that took Fireteam Osiris to Genesis.
 * Samuron Guardian: This Guardian took a Pelican holding Marine Selena Rhodin from the planet Samuron.
 * Kamchatka Guardian
 * Sarcophagus Guardian: This Guardian was disabled by the Huragok Prone to Drift. Although ostensibly present on Onyx (aka Trevelyan) to supervise its initial construction long ago, it is unknown why the Forerunners would have installed such a construct on one of their most secure facilities, in light of what is known about Guardians' purpose.
 * Guardian 3209: This Guardian inadvertently carried an M820 Scorpion from its point of origin to Genesis.

Behind the scenes

 * A Forerunner construct called "the Guardian" was originally set to appear as an enemy in a Halo 3 campaign level that later became a multiplayer level Guardian. It was stated that the player would have been able to rip out the Guardian's eye beam and use it as a weapon in the campaign level. According to Art of Halo 3, "The Guardian evokes memories of Compilers (from one of Bungie's previous games, Marathon) and the robes of a High Court Judge - which is fitting because, as anyone who has encountered them can tell you, their judgments are swift and final, and their logic utterly alien." While they were not seen in the final game, their design was later used in Origins for two Forerunner constructs seen escorting a Keyship to the Portal at Voi.
 * An early version of the Halo 5: Guardians incarnation of the Guardians was first seen in the Halo Xbox One announcement trailer and later in the bookend cinematics of Halo 2: Anniversary, with the final design revealed in promotional artwork. There was considerable speculation as to the nature of the constructs prior to the confirmation of them as the titular Guardians in Game Informer's June 2015 issue. When asked about the construct seen in the Halo 5: Guardians key art on Twitter, the game's Creative Director Josh Holmes alluded to the name by replying that "The answer is in plain sight."

List of appearances

 * Halo 2: Anniversary
 * Hunt the Truth
 * A Hero Falls
 * The Hunt Begins
 * Halo 5: Guardians
 * Halo Mythos
 * Halo: Fractures
 * What Remains
 * Rossbach's World
 * Halo Wars 2
 * Halo: Legacy of Onyx
 * Halo: Bad Blood