According to TimeSplitters, Planet X was discovered by Humans, in the Gamma Sector, at some point between 2005 and 2020. The Timesplitters game manual also states "...play different characters in different locations spanning a century from 1935 to 2035." Since from our perspective, 2020 is not a realistic date for interplanetary travel by humans, one school of thought has arose that the date of 2020 provided may be inaccurate, and that a date close to 2200 may seem more appropriate. However, the provided dates could instead be taken at face value, for the concession that the events and timeline(s) of the TimeSplitters universe are not our own.
- Main article: Planet X (Story)
In 2020 (possibly 2200), Planet X was the scene of an operation by humanity to recover a stolen cyberbrain that was being held hostage by several alien species: the Green Aliens, Pillar Aliens and Red Aliens. Soldiers Sebastian Photon and Angel Perez were sent to recover the cyberbrain, and successfully extracted it.
- Main article: Return to Planet X
- Main article: Planet X (Arcade)
This is considered to be the largest Arcade map in the TimeSplitters series. It is based on the map used in the 2020 story level, but with some walls removed to allow easy access. It features a large landscape, with many tunnels and an underground alien base. The most memorable feature of the map is a huge waterfall with flowing green water (which can also be seen near beaches on Return to Planet X). The map is also one of four to feature the Last Stand game mode, in which the player must protect four purple crystal formations using a turret.
- Main article: Ufopia
Ufopia is an arcade map based on Return to Planet X. Although it features no areas from the story mission, it is considered to be a large, floating alien hangar for UFOs. The base consists of a maze of corridors and hangars, as well as a few areas outside the main body of the ship. The map is the only one on TS2 not to appear in any Arcade League match or Challenge, but is considered to be great for games of Virus, due to many winding corridors and holes, which may be useful for a quick escape.
Although there is no Mapmaker tileset actually called 'Planet X', the 'Alien' tilesets on both TS1 and TS2 are considered to be based on the planet. On TS1, the tiles mainly consist of corridors of similar texture to the cliffs and tunnels of the Story/Arcade map. On TS2, the tiles are of a sterile, white spaceship, similar to the interior of the larger UFOs on Return to Planet X. The default weapon class is also similar to R.T.P.X. and Ufopia.