Reclusive Time Lords, watching over all of time and space, what's their game? Gallifrey
We first learned of Gallifrey at the very end of the 2nd Doctor's time when, in the conclusion of The War Games, The Doctor had to appeal for their help. After which The Doctor was exiled to Earth for a couple years. Since then we've learned more and more about Gallifrey as tidbits here and there have been revealed in episodes.
