Erebus was the only planet located beneath the Eye of Atheatos, within the Occlus sector. The world had proved to be of exceptional and significance throughout galactic history, serving as the homeworld of the Charon people, the capital of the Charon Dominion, the only planet within the interstellar sector of the Hellmouth, and the greatest military stronghold of the Extant War. To the vast majority of the galaxy within realspace, Erebus served more as a myth than a reality, due to its inaccessibility through the other side of the Aperture, fortifying the legend and fear of the Charon.
Due to the Otherspace galaxy's lack of consistent stars and constellations, the world of Erebus was shrouded in near-perpetual darkness, visible only due to the Lake of Fire, a colossal nebula that spanned through the Erebus system, and as a result of its gases, also made the Eye of Atheatos visible to the naked eye.
Although much of the planet's surface was developed, the vast majority of Erebus' urbanization was beneath the planet's surface, which was was cities, temples and other structures were carved. The world of Erebus possessed only one moon, Nyx, which was where the original Charon discovered the last legacy of their Kathol precursors; the world-annihilating superweapon known as the Atercor.