LV-426 (Earth-9791)

"Acheron is a dim twilight, its night is darker than the farthest reaches of interstellar space, because not even stars shone through its dense atmosphere to soften the barren surface with twinkling light."

- - Famous UNSC poem

LV-426, also known as Acheron, is one of three natural satellites of the gas giant Calpamos, in the Zeta Reticuli system. Formerly home to forerunner presence, it was the home to a mysterious derelict vessel that carried xenomorph Ovomorphs.

Prehistory
Approximately 2 million BCE, a ship belonging to a member of an ancient species crash-landed on Acheron, holding multiple xenomorph Ovomorphs for unknown reasons. The pilot died, apparently impregnated by a Facehugger, but not before sending a warning message for any sapient explorator to not approach the ship.

Human discovery
Acheron was first discovered by humanity on May 14th, 2525, when the Office of Naval Intelligence observed and cataloged it by a slipspace probe. The initial comprehensive survey would only be carried on 2531. When ONI discovered the moon, they also detected a mysterious transmission hailing from the derelict vessel, where they found out about the xenomorph species. With the threat of annihilation of the Insurrection, ONI sought to use the alien creature as a bioweapon in order to ensure the survival of the human race. The agency then sent Ash, a synthetic operative, to replace and pose as a crew member of the Weyland-Yutani Corporation's freighter Nostromo after a routine delivery on the outer colony Thedus, and land on the moon to acquire a xenomorph.

The Nostromo landed on Acheron on June 16th, 2528 after acquiring the signal from the derelict at Acheron, as per Weyland-Yutani protocol. Despite the fact the ship's Shaw-Fujikawa translight engine was damaging during the landing, Captain Arthur Dallas, First Officer Thomas Kane, and navigator Joan Lambert formed a trio to explore Acheron's surface, eventually discovering the derelict and the signal coming from it. While they explored the ship, the trio discovered the fossilized remains of the ship's pilot and the many Ovomorphs that were stored on the ship for reasons unknown. Once Kane approached them, he was attacked and impregnated by a Facehugger. Dallas and Lambert then took Kane back to the Nostromo, which departed from the moon. Hours later, the xenomorph that had been incubated on Kane birthed aboard the ship, leading to the massacre of the crew and the destruction of the vessel.

ONI exploration
Despite the tragedy and failure of the Nostromo expedition, the Office of Naval Intelligence continued on their attempt to capture xenomorphs from the moon. On June 1st, 2536, Aegis VII salvagers Russ and Anne Jorden were hired by ONI as expendable fodder to explore Acheron and bring Ovomorphs to one of their facilities on Paraíso. The resulting expedition led to the couple being attacked and impregnated by Facehuggers upon their arrival on the colony, leading to a massive outbreak that had to be put down later on by the UNSC one month later; most of the colonists and UNSC Marines died during the assignment.

Aftermath
After the loss of the Nostromo and its crew, the incident was covered by the Office of Naval Intelligence, and the Nostromo declared 'lost with all hands'. Years after, on September 29th, 2547, the warning beacon was deactivated by the salvaging vessel Anesidora, further placing Acheron in obscurity. During their expedition, crewmember Catherine Foster was attacked and impregnated by a Facehugger, which later matured into a grown xenomorph aboard Sevastopol Station.

Terrain and climate
"It's a rock. No indigenous life."

- - Paul van Leuwen Acheron has an equatorial diameter of 12,201 km, maintaining a surface gravity of 0.86 and a rotational period of 2 hours. The crust of the moon is composed of aluminium silicates, as well as magnesium intrusion, which, once in the surface, is manifested as lava flows of basalt, rhyolite, and microgranite. The moon was seemingly home to volcanic activity in the past, which can be seen by the surface, which does not exhibit any tectonic activity. The gravitational shift generated by Acheron's arrival in the Zeta Reticuli system, possibly 40 million years in the past, is theorized to be the cause for Calpamos' rings.

The atmosphere of the planet is highly toxic to humans, consisting of nitrogen, methane, water vapor, and carbon dioxide, as well as small concentrations of ammonia. The surface is subject to strong winds, but it is not big enough to sustain a big, deadly storm.

Geographical features
Acheron possessed a mountain range named the Illium Range by the Office of Naval Intelligence, notable for being home to the abandoned Derelict spacecraft.

Acheron is absent of indigenous life forms, with only the Ovomorphs that lied aboard the derelict remaining in stasis. According to the subsequent survey ran by the Office of Naval Intelligence, Acheron was a "dead rock".

Locations

 * Derelict

Trivia

 * The moon is named after the Acheron river in the Epirus region in Northwest Greece.