Cernon

Long ago, an ancient civilization gathered an extreme about of trash. With nowhere to put it, they shot it all into space. Bacteria survived inside in air pockets, and little by little the trash sphere decayed and compressed until it became a planet with it's own atmosphere. This planet was named Cernon by the inhabitants.

Cernon never developed plant life. Every living being on it's surface is an animal. Beneath the surface, microbes eat the soil and produce the gases that the animals breathe. Anything that looks like a plant is a slow animal. Because there is no plant life, there are very few places to hide, so instead of hiding life on the planet gagues what is ripe for the killing by seeing how weakly it's moving. This leads most imhabitants to attack anything that stands still. It also encourages hyper aggression in the local wildlife. Once the Cernonians made contact with the rest of the universe, the planet was classified as a biological threat and sealed inside an energy barrier. Entry and exit from Cernon became heavily restricted ever since.

Atmosphere
Ceron is a very dry climate, only slightly moister at the poles. The atmosphere has high levels of both Oxygen and methane. This leaves the sky mostly blue with a slight greenish tint. However the air is not particularly thick so if you squint you can see stars in the daytime.

Wildlife
The swarm

Cernon's most threatening wildlife, 'The Swarm' is the translated name of the Cernon language. Key to it's name, the Swarm is a loud of small bat-like creatures which can fly at rather fast speeds. They have two rows of sharp teeth which they use to tear apart still-living prey. If a natural disaster strikes and there are any survivors, they will replicate and mutate any others it finds to give them the traits that allowed it to live. The swarm is also known to be psychic, projecting messages into the heads of their own kind, leaving only a faint sound in it's wake.

If an individual is in danger, the entire swarm will always rescue one of their own. The only other creature on the planet who has this sort of behavior is the Cernonian people.