Kingmaker

The Kingmaker was a mysterious woman who lived in a cave in Mount Plutarch. She claimed to guard the Time Lords, as the Time Lords guarded time.

She could grant budding young Time Lords their TARDIS, although whether all Time Lords underwent this ritual or only members of the Fraction is unclear. She had no interest in morality and did not stop the Time Lord Tannis from killing as he did not use the power. After the Doctor appeared to kill both Tannis and himself, Ace returned to the Kingmaker who told her that there were no more Time Lords, but also pointed out that the Doctor's body was not found. (WC: Death Comes to Time)

It is left ambiguous as to what the Kingmaker is. However it is implied she is a being with greater powers than even the Time Lords, as she addresses the Doctor as "you and your kind". This has yet to be explored on screen or in spin-off media.