The Anatomy of Halo

Created by the Forerunners over 100,000 years ago, Halo was designed to be a wide-effect, neural-disruption weapon capable of destroying any sentient life which might perpetuate the Flood Parasites’ existence. But this wasn’t Halo’s sole function. The enormous Ring-world was also a structure ten thousand kilometers in diameter engineered to support life on its interior surface. This part of Halo’s architecture is believed to be of roughly the same constitution of a typical One-G planet, with large geographic formations and enormous bodies of water. All of this contained within a climate-controlled bed of atmosphere roughly 318 kilometers from one edge to the other. While intel suggests that the seven Halo Installations representing the array each have their own distinctive environment conditions, the two best-documented installations, 04 and 05, offered a large assortment of flora and fauna across their surface. Towering mountain ranges, enormous canyons, and vast swaths of desert terrain occupied their interiors, comprised of a rich intermingling of ecosystems. To the untrained eye the facade of these ring-worlds looks no different than that of many life sustaining planets. Unsurprisingly, given their origin, the surface of a Halo ring-world is littered with Forerunner structures and technology: enormous beacons, soaring spires, and immense complexes. Still, for the most part, these individual structures’ overarching purpose and mechanism remain a mystery. And underneath Halo’s outer strata exists a honeycomb labyrinth of interior structures, interconnected by bridges made of hard light, complex tunnel systems, and a vast teleportation grid. The surface of Halo is no small marvel: its majestic architecture, its natural composition, and its sheer size offers only a hint at the Forerunners’ technological mastery.

Halo installations are vast superstructures roughly 10,000 kilometers in diameter. As expected, a construct of such size demands an on-site system which can offer visitors both locational and directional information. And therein lay the origins of the Cartographer. While the term "map room" refers to the specific compartment where the holographic map projection is generated, the Cartographer is, in essence, the entire complex which remains in constant communication with all parts of the ring. Unlike typical maps, the Cartographer is not bound by changes in structure of the ring, or its general performance, which is perhaps why the facility itself is referred to as a "map-maker". Every projection is in real-time and reflects the ring's precise state at the moment it is queried. When accessed by an artificial intelligence, it can be manipulated to an even greater degree of accuracy, identifying critical risks, and providing waypoint indicators where needed. Protecting the Cartographer are a number of security measures developed to prevent access by the Flood or another hostile species, safely locking the map room proper deep within the facility. The Cartographer's importance is unquestionable, as it provides all those who access it with the location of Halo's control room and the mechanism to fire the rings: the Library's Activation Index.

Deep within Halo, and protected by immense chasms and heavily fortified walls, is the enormous research facility known as “The Library”. As with other locations on Halo, the Library’s interior is a catacomb, a series of corridors and tunnels extending outward from a centralized hub. Outside the structure a vast gondola system interconnects a heavily guarded perimeter, while inside, a series of elevators gives those who enter it access to every one of its many levels. These dense but clustered compartments distributed across the structure’s enormous frame allow the Library’s array of gliding sentinels to maintain and secure the site with relative ease. Accessible through numerous terminals and peripheral systems are the facility’s archives, an immense data-base holding the Library’s numerous caches of information. This data ranges from the genetic sequencing of many species acquired throughout the galaxy to accounts of the Forerunner governance and their centuries-long war against the Flood. As would be expected, knowledge on the parasite itself exists within the Library’s data-banks, though much of the actual research occurred within separate containment facilities buried deep within the ring. And at the apex of this structure is the facility’s most important mechanism: a key, known as the Activation Index. When reunited with the control room’s core by a Reclaimer, a human, the Halo ring would send a harmonic pulse throughout the galaxy, triggering the other six rings and destroying all sentient life within range. As the Forerunners prepared to fire Halo 100,000 years ago, they enacted an effort to save and catalogue as many sentient species as they could, providing shelter for them on the Ark in the event of the Array’s activation. The final stage of the conservation measure would result in these saved species eventually being returned to their to their own homeworlds: a single sweet note in what was otherwise a dark, and ultimately devastating reality. For this reason, the Library and its activation index were of great importance to the Forerunners’ plans, and they remain extraordinarily significant in the context of the array.

While a Halo Installation is typically under the supervision of a single Monitor, or caretaker, the enormity of its process requires numerous automated drones. These machines are commonly referred to as Sentinels. Sentinel operations meet a wide variety of ends: whether it’s the repair of damaged structures, the mining and retrieval of raw material, or most importantly, the containment of the Flood parasite during an outbreak. For this reason, the design and size of Sentinels varies as well: from the small, flitting Constructors to the heavily-armored Enforcers, and even larger Retrievers, gigantic strato-sentinels which strip-mine resources sites for the rings’ construction. Held aloft by an anti-gravity system which makes the buildings mobile, large Sentinel production factories hover high above a ring’s surface, safe from the Flood. Though Sentinel assemblage facilities do not have the same significance as other sites on the Halo Installations, their relative importance in the event of a Flood outbreak can not be ignored. Records indicate that during combat on Installation 05, also known as “Delta Halo”, the Flood targeted the Sentinel factory, using captured Covenant weapons to bring it down. This event served as a sobering reminder of the necessity of sentinels to maintain a Flood outbreak, as well as the insidious and intelligent nature of the parasite itself.

Prior to the firing of the Halo Array, dormant specimens of the Flood were captured and contained for research as per Forerunner protocol. The Forerunners recognized that because the origins of the Flood was mysterious and elusive, it was entirely possible that the parasite might one day resurface in the Milky Way Galaxy. So rather than simply fire the Halo Array, they took the risk of securing specimens and keeping them dormant in containment facilities buried deep within the Halo rings themselves, their hope that one day a cure could be discovered and the Flood’s threat nullified. These containment facilities may vary per ring, but all incorporate numerous safety mechanisms and security systems to ensure that they are not easily unlocked. Accessible through a bunker-like aperture and by way of a deep elevator shaft, the Flood containment facilities were further hidden behind many locked doors and many advanced security protocols. There, the Forerunners could observe individual specimens of the Flood, captured during the course of the war and held in suspended animation, as well as studying them within environment generated by the parasite. Some research sites were even held high above the ring’s surface, locked out in a remote and inhospitable environment, like the clefts of a frigid mountain side. With foresight that even these advanced precaution could be compromised, the Forerunners established and distributed a litany of alternative restraint systems designed to limit the Flood’s movement across the ring. A series of large defensive walls and immense chasms would divide the surface of Halo, the latter typically only traversable through the activation of a hard-light bridge, and, by Forerunner design, the local weather systems would aggressively batter the contaminated portions of the installation with frigid and inclement weather in an effort to slow the parasite’s collective growth. In the end, despite all of these efforts, the Flood would still escape. Containment on both Installation 04 and Installation 05 would fail, and the Flood would once again threaten the galaxy, halted only by the sacrifice of a brave few.

Easily the most important aspect of any given Halo installation, the Control Room is the location where the Halo Array is activated and fired. In order for this to occur, a Reclaimer, or human, must first acquire the Activation Index located in the Library facility, then reunify the index with the Control Center’s Core. Though both of these require the actions of a Reclaimer, the Index itself can easily be transported by any individual or artificial intelligence. Recognizing its vulnerability should the Flood ever escape, the Forerunners typically designed the Control Center to be an extravagant citadel, heavily fortified and well defended. Accessed by traversing a number of corridors and gates, the Control Room proper is generally a series of platforms focused on the holographic representation of the Installation and any nearby planetary bodies. The Control Center is visually the most impressive of Halo’s facilities, tapping into the looming, angular qualities of Forerunner design. But even there physical shape cannot compare with the latent power the Control Room contains. At the center of this room is usually a pedestal representing the Core, into which the index is inserted to activate Halo. Once reunification is achieved, the Ring prepares to amplify its neural disruption effect by way of three phase pulse generators, allowing it to fire deep into space. Though their firing mechanisms can be tunned to specific ends, the Array’s individual rings are engineered to fire up to 25,000 light years in every direction, transmitting the pulse effect to other installations which initiate their mechanisms in response. The result: complete eradication of all sentient life within the galaxy, an act which was initiated only once, a hundred-thousand years ago. If the activation sequence is interrupted on any ring, a fail-safe mode is triggered and superluminally communicated to all installations. When this occurs, the Halo Array’s fail-safe can only be reset or fired from one location: Installation 00, also known as the Ark. This very event took place after the Arbiter and Commander Miranda Keyes prevented Delta Halo from firing, forcing the struggle for Halo to the Ark, where the Covenant and the Flood would finally meet their end.