Autum is the only major moon of the planet Illum, tenth planet of the Indicum System in the Ambrosia Galaxy. And the secondary member in dual-planet system with it. It is a cold D-Class world, and was also the former eleventh planet of its home system.
Autum is a cold desert world, its dynamic surface is filled with hills, mountains, canyons, dried lake beds, impact craters, and lava flows. Fossilized unicellular and multicellular life dots the surface as well.
The moon wasn't always the cold desert world we see today. Originally, it was a temperate Terra planet with life covering its entire surface. However it would be captured by its sister world Illum's gravity, hurling it into its orbit. Once in close proximity of Illum, the two bodies would inflict tidal forces on each other, heating both bodies up significantly. This would melt the former ice planet Illum turning it into an oceanic world, while Autum's oceans would evaporate, killing all the life that inhabited the surface and creating a cold desert spanning the entire moon.
Despite the evaporation of its surface water, the moon's tectonic plates are still active. This means the moon has natural volcanic activity and contains one continent named Etitum. It also holds its own magnetic field independent of Illum, this has caused the binary system to have a large magnetic field that stretches across the entire star system.
It holds one mid-sized colony named Tronta Station, with a population of 700,000 people. This colony doesn't serve any distinct purpose, instead it exists due to Autum being one of the few relatively habitable bodies in the Indicum System.
Autum formed alongside the formation of its parent star Indicum around 1,178,000,000 BCE. When it first formed, it was the eleventh planet of the Indicum System and in its early years it existed as a hot, desert world. However throughout hundreds of thousands of years it would cool down and allow for liquid water to flow on its surface.