The Oubliette of Eternity was one of the darkest secrets of the Time Lords' Celestial Intervention Agency. It was a device installed in a chamber that was used to disperse criminals convicted of high treason, accomplished by supposedly erasing them from history so that they never existed, but was also used to dispose of Gallifreyans who learnt of its dark secrets.
Victims of the Oubliette were erased from history, as well as memory, but rather than being erased, it cast them into the universe of anti-time and transformed them into Neverpeople. (AUDIO: Neverland)
Upon finding Janartis in the House of Heartshaven, Romana II commented that she'd thought he'd been "oublietted." (AUDIO: Panacea)
When Narvin first became Coordinator of the Celestial Intervention Agency, he asked permission from the President of the High Council of Time Lords, who was Romana II at the time, to use the Oubliette on the planet Bellascon. (AUDIO: Erasure)
In an alternate universe where the Time Lords sold their technologies to other races, they gave the Oubliette of Eternity to the Galyari. (AUDIO: Reborn)