Tethys III was the third planet in its star system. The planet was a hydrogen-helium gas giant with a frozen helium core. This planet was located several hundred light years away from the Ngame Nebula.
In 2367, the crew of the USS Enterprise-D used the planet as a basis for concealing the Paxan homeworld in a T-Tauri type star system located within the nebula. (TNG: "Clues")