Acheron

Acheron, CelWP M5 b, or XM 336 b is the only planet around the black hole Abyss. Acheron is a small, cold rocky planet, with a thin sheet of ice on the top, and was added in CelWP Release 7.

Characteristics
Acheron is a small cold Pluto-like planet. Due to its small size, it lacks any form of atmosphere, and even if it was much larger, all the atmosphere froze out anyway. Acheron lacks any major moons and is pockmarked with craters, collected over the eons from Abyss' thin asteroid belt. Acheron is a uniform light gray color, with almost no contrasting albedo features.

In summary: BORING!

However: during the supernova of Abyss' progenitor star, Acheron, which actually used to be a freaking gas giant, received a huge dose of heavy elements, formed through the R-process of fusion that takes place in supernovae. This made it a great place to mine for materials, and soon, despite its remote location, it was filled up with large mines and stuff, and cities to support the mines, and large railguns and mass drivers to shoot the material out of the solar system to the Eridonian Union core.

History
Acheron formed around Abyss' O-type progenitor star as a large gas giant, extremely hot. However, when the star went supernova, all the gas, and most of the rock on the core, got blasted away, leaving a small, half-earth-mass planet. However, the supernova also gave this small gas giant core a large supply of heavy metals, just formed in the supernova itself. Later, when the New Eridonian Union (see the Civilizations article) started exploring the region beyond the Evolution Cross, with the Strange New Worlds probes, one of them came across the Abyss system, adjusted course to rendezvous with the planet, and saw the motherlode of rare metals, and then the Union came rushing in to establish the system under their control and mine the hell out of it.

Another reason the Union wanted the system was because it served as a bottleneck between the Eurak Republic and the Union, as all warplanes between the two empires converged here, allowing for a easy blockade against ships that may have tried to invade. However, this was unnecessary (so far), as the Union and the ER have good relations, but... just in case?