Etra Prime
From Tardis Wiki, the free Doctor Who reference
Etra Prime was the oldest planet in the known universe.
The Daleks removed the planet from time and space so that they could mine the Apocalypse Element from it. Twenty years later, the Daleks sent Etra Prime on a collision course with the planet Archetryx, which was hosting a temporal treaty attended by twenty of the Temporal Powers. (AUDIO: The Apocalypse Element)
Planet One (TV: The Pandorica Opens) and Chrone were also said to be the oldest planet in the universe by some. (COMIC: The Vortex Code)
