Io

Io was a volcanic moon in orbit around Jupiter. It was the home world of the Jovian Empire and where the Church of the One migrated to after leaving Mars. Despite its high volcanic activity, it was the most habitable of Jupiter's four moons due to a blotched terraformation attempt, although it was not inhabited until the followers of Titus moved there.
== Description ==
Before humanity's attempted terraforming, Io was a bright yellow color and covered in volcanoes that spewed lava hundreds of miles into into its atmosphere. During terraformation, Io's soil was turned into black obsidian and its lava was exposed to elements turning it pure white.
Io had a varied landscape, some parts a scathing tundra perfect for cities and agriculture, others jagged and uninhabitable due to volcanic activity. The obsidian glass that made up most of the ground was completely flat in some areas, but shattered into a fine grain in others. Many of the mountains and jagged cliffs were from massive pieces of obsidian cracking apart and falling deeper into the moon, creating huge shards that pointed thousands of feet into the air.
In places where agriculture was common, people often below the obsidian to reveal the planet's original yellow soil, which was ripe with sulfur and other nutrients that were essential to farming. This sulfur's odor could be smelled everywhere on the planet.
Due to the moon's proximity to Jupiter, the planet hung in the sky for most of the 408-hour long day. Only a quarter of the day was spent facing away from Jupiter, during which the sun was the only light in the sky. Due to its distance, it was more akin to the Moon's affect on Earth. When the moon was on the far side of Jupiter, the sky was completely dark save for the stars. At this point of the orbit, only geothermal activity heated the moon. 
The volcanoes of Io were some of the most dangerous places in the solar system. Streams of white lava poured from underground pools and tunnels, toxic gases rose from the ground, earthquakes were frequent, the obsidian ground could easily shatter and send adventures into fatal falls, and cooled lava that turned black and easily blended in with obsidian was everywhere. Due to the hundreds of volcanoes on Io, black ash blanketed the landscape and frequently fell from the sky.
No plant or animal life survived the attempted terraform, and the only tangible reminder of the terraform were petrified dead forests scattered throughout the landscape.