Regos

Regos is an abandoned moon where the tragic events with the Regos Exploration Crew took place. Not much is know about the moon due to the only people setting foot on it having to leave the exploration almost immediately. But we do know it's home to only only species & It's a very cold & inhospitable place. All people who have explored the planet needed heavy space gear just to be able to survive its treacherous freezing climate & nearly non-existent atmosphere.

Atmosphere
Regos is extremely cold, allowing very little life-forms to ability to survive there. It also has little to no atmosphere either, meaning not even the most durable of lifeforms could survive there.

Biosphere
Regos is abandoned...Nearly. It has no lifeforms on it except for the Xycheles 001 who people assume moved over to the abandoned rock to get away from other lifeforms. It worked too as other than the Xycheles' City (which has a large shield surrounding it, that can blend into the planet making the city practically invisible) there are no signs of any lifeforms on the planet.

Geography
Since it is a moon, with nearly no atmosphere, it is constantly being pummeled by asteroids & other space objects, making for a very rocky, & bumpy terrain.

History
Regos was targeted for an exploration due to it never being explored before, & being so close to the mission leader's home planet. Space Commander wanted to see if there was anything of value on the moon. So he grabbed a crew of highly skilled space explorers for the job. The mission went horribly wrong as almost immediately after landing, as the crew (minus the leader who stayed back with the ship & was killed) stumbled upon a massive alien city, hidden on the moon all this time. They return to the ship, see their leader dead, & fuel canister stolen. They had to return back to the city to find the fuel. Upon arrival, another member was killed by a Xycheles, and Spaceionaut Spikaww (the second in command) barely escaped from the city with the fuel, by flying over the gates with a jet pack, returning to his ship before the Xycheles could catch him, and rescuing the crew.