Halo Installation 02

Halo Installation 02, also known as Epsilon Halo, is a Halo fortress-world located in the Galar system of the Sagittarius Arm.

Diluvial War
Installation 02 was constructed in the Foundry of the Ark at some point prior to 97,445 BCE, during the Diluvial War. It was transported through slipspace following completion to its present location, and it and the rest of the Halo Array were activated by the Didact, killing all sapient life throughout the Milky Way Galaxy. Following this, Epsilon Halo was used as a regional staging ground for the Reseeding of the galaxy. Once this was completed, the Forerunners transferred all control for its core functions related to the firing of its main weapon to Reclaimers, and departed the galaxy.

Post-Firing and Possible Attack
Although initial estimates by UNSC researchers assumed that Epsilon Halo, like its peer installations, had led a fairly quiet life, documents recovered by 343 Guilty Spark and the AI Cortana during the Battle of the Ark have completely disproven this theory. Instead, reports sent to the Ark showcase that the monitor 07 Contrite Witness had completed an overhaul to the fortifications for the Halo's quarantine zone and Flood research laboratories around 81,400 BCE. This was apparently in response to the troubles experienced by Halo Installation 05; something apparently validated during a suppressed parasite outbreak in 78,100 BCE.

Some sort of cataclysmic event occurred sometime around 62,800 BCE, of which the details are sparse as not all the reports were fully compiled by the time the Fleet of Retribution left the Ark. Whenever it was attacked or simply suffered a catastrophic failure is largely unknown, but this resulted in the installation's first partial-strength firing since the events of the Diluvial War - and the only Halo to have two successful activations to its name. Whatever occurred had apparently damaged the megastructure, prompting the Ark to dispatch replacement parts as well as reseed that portion of the galaxy. No other details have since emerged about the Halo's activity since then, other than what affected the rest of the array.

Human-Covenant War
In 2552, with the destruction of Alpha Halo, Epsilon Halo moved to elevated security status, and with the aborted firing of Delta Halo prepared itself for immediate firing. It had begun charging upon receiving the authorisation order from the High Prophet of Truth in the Ark's Citadel, but fortunately the process was cancelled when he was defeated by John-117 and Thel 'Vadam.

Surface features
Unlike most of the Halos, whose surfaces tends to be dominated by continental landmasses, Installation 02's surface is covered by a vast saline ocean which occupies almost 98% of the ring's total habitable area. Reaching a maximum depth of 9.2 kilometers, the waves are powered by a sophisticated array of deep-ocean currents that run lengthwise along the Halo, creating a complex energy funneling network that regulates the temperature of the megastructure. No single current runs for more than a third of the way around its circumference, as hadopelagic trenches and vast subterranean mountains disrupt them and facilitate the creation of newer, short-lived currents that rise up to the surface. It is highly suspected that these obstacles are deliberated placed to encourage the development of unique ecosystems and oceanic biomes, and indeed their presence guarantees that each subsection of ocean is unique in terms of oxygen content, nutrients, and even the chemical salts suspended within the water. While most sea currents are authentic in terms of their natural processes, there are some distinctly-artificial vents that continue to drive its heat and subsurface weather cycles during intense freezing conditions, which direct flow using modular jets.

Even so, it appears that Epsilon Halo does have small, isolated pockets of water that are cut off from the surrounding ocean through artificially-constructed walls that rise out of the waters, with solid glass-like roofs connected across the top. These appear to be impromptu experiments conducted by the monitor to explore more exotic forms of life, including ammonia lakes, extremely-low temperature environments, and even replicate the vacuum of space. Whenever this was mandated by the Forerunners for the Halo's research, or something the monitor did out of boredom, ultimately cannot be known without dispatching a team to the ring itself.

The next largest portion is composed of immense frozen formations of ice, which expand and retract within two-year cycles. There are three permanent ice sheets on Epsilon Halo, all located in its northern hemisphere. They are grafted on to the walls of the Halo, and they all exceed two kilometers in thickness - enough to touch the sea floor and still be more than five hundred meters higher than the ocean's surface. In addition, at least 32 seasonal ice sheets will grow and shrink throughout the year, which are centered over the few landmasses on the ring. The rapid melting of these regions creates tens of thousands of glaciers that undergo a mass-calving event that sends icebergs across the ring at regulated intervals. It is believe that this phenomena is an artificial mechanism used to keep the temperature controlled during the boiling summer months, and to reduce the shock to the creatures that call it home. The ice usually dominates a maximum of 35% of the surface area during the winter months.

Archipelagos of small islands, typically the peaks of seamounts, are the final piece of the ring's surface. These regions can be incredibly diverse over a relatively small distance, with volcanic basalt islands, dry scrublands, accumulated sandy banks, and even tropical rainforests can all be found in the span of a few kilometers. Each island exhibits its own special, unique appearance, as flora and fauna evolves independently to the rest of the surface. That said, the terrain is not truly randomized, and there are many regions that are devoted to a specific form of environment. Interestingly, each island is not entirely solid. All have large cave systems that descend into a central area that mimics their ideal environment, to provide shelter during harsh climatic events. Most islands boast some sort of Forerunner structure, with more still freely sitting above the water, held up by vast bases that stretch up from the ocean floor. These could give researchers the unique chance to examine completely-excavated structures found on the other rings. Even these structures, as clean as they are, still boast their own forms of wildlife found no-where else in the galaxy.

Nearby points of interest

 * Pesegem Slipspace Tether - Located within 60 lightyears of Installation 02, the Pesegem Tether acts as a possible way for humanity and the ex-Covenant species to potentially travel to the Halo, provided a working equivalent could be located in the Orion Arm.