Sanghelios

Sanghelios is the homeworld of the Sangheili, and was one of the most influential worlds in the Holy Ecumene.

Primeval Period
During the 3rd millennium BCE, Sanghelios enjoyed an age of unprecedented technological advancement and societal progress. Gleaming megacities supported a planetary vast population, with a growing number of Sangheili living in orbital habitats and even a handful of off-world colonies. This period, known as the Age of Decadence by latter-day Sangheili, was brought to a screaming halt around 2,300 BCE. Although records of what exactly happened are now lost to history, some sort of experiment caused the Shard of Heaven to malfunction. This triggered the Skyfall: the early orbitals of Sanghelios were wrecked and came crashing down on the surface, and most higher forms of technology ceased to work. Millions were killed in the first day alone, and far more perished in the days, weeks, and months, as the disaster expanded in scope with the collision of asteroids and comets previously held in place. To say that the Sangheilian disaster-relief procedures could not cope was a significant understatement. They had been reduced back to a pre-space age civilization, and their colonies throughout the system were forced to fend for themselves. Without support from Sanghelios, most of the smaller outposts died out, with significant populations maintained only in the best-established colonies.

Though the Sangheili eventually recovered, the Sangheili were permanently affected by the event. Not only did it showcase the power that inert Forerunner god-machines held, but it also saw the disappearance of their most holy artifact. With their belief in science shattered and so much trauma inflicted, many turned back to religion to cope, in particular one belonging to a state that had always opposed reliquary experimentation. By the time the Sangheili returned to space so many centuries later, it was with a conservative, deeply-traditional culture.

Satellites
Sanghelios is encircled at the equator by an orbital ring known as the Silver Girdle. This complex of facilities, which dates back to the Covenant's late antiquity, houses many of the planet's orbital ports, spacedocks and shipyards, along with a number of planetary defenses. Numerous gravitic sky-lifts link to the structure from the surface. Other than the Silver Girdle, Sanghelios is surrounded by a swarm of stations both civilian and military.

Suban
The larger of Sanghelios' two moons, Suban hosts a significant colony dating back to the earliest days of Sangheili space travel. It is most notably the source of the Subanese crystals used in Covenant shard weaponry. The production and harvesting of the crystals is monopolized under the Subanite Brotherhood, which holds enormous wealth due to the importance of their export and acts as the de facto government of the moon.

An ongoing cause of concern and public debate regarding Suban is the moon's decaying orbit around Sanghelios. Since the effect was first documented by astronomers in the centuries following the Skyfall, it is commonly attributed to the destruction of the Shard of Heaven, the Forerunner satellite supposedly having maintained the stability of the moon's orbit. However, some older records are recorded as having observed the moon's irregular orbit even long prior to the Skyfall. Whatever the case, tidal effects on the planet have been slowly increasing over the last three millennia, and the moon is expected to hit the Roche limit within the next 30,000 years. Without intervention, Suban will be disintegrated by tidal forces, along with apocalyptic tidal effects on the Sanghelios even before the moon directly collides with the planet. Various efforts have sought to stabilize Suban's orbit, but even with the Covenant's exotic drive technology, the moon is far too massive for their drives to make a difference. A brute-force solution involving the construction of a vast reaction engine has been proposed, but the scale and cost of such an undertaking has meant the idea has not, as of yet, left the planning stage. Instead, many Sangheili hope salvation will come in the form of an extraordinarily powerful Forerunner engine, and multiple Sanghelian statesmen throughout history have sponsored expeditions to find such a relic. So far, these efforts have not born fruit.

Qikost
A moon largely covered in oceans, Qikost is a notable aquacultural site for the Sangheili and home to various population centers. Its oceans have served as a major source of deuterium for fusion purposes since the Sangheili's early spacefaring days.