Etarho

Eta Rho was a gas giant. Its name was derived of letters in the old Greek alphabet: "eta" and "rho". The Valeyard claimed that the Doctor, in his final incarnation, spent some time on a satellite orbiting Eta Rho, trying to break the twelve-regeneration limit imposed by Rassilon on the Time Lords.

Inquisitor Darkel brought Space Station Zenobia into orbit around the planet when putting the Valeyard on trial, but it was placed in a displaced timeline to hide it. (AUDIO: Trial of the Valeyard)