Hecuba

Hecuba (also known as the Queen of Time) was a powerful being who ensnared sentient beings in games related to time manipulation, with their freedom as the stakes. She was the sister of the Celestial Toymaker.

Nature and powers
The powers of Hecuba were similar to those of her brother, but while he was fond of childish games, her games and traps were related to time and clocks. (AUDIO: The Queen of Time)

Her brother, the Celestial Toymaker, once claimed to be the embodiment of one of the fundamental forces of the universe, much like the Guardians of Time. Whereas the White and Black Guardians personified the absolutes of morality, however, the Toymaker was the avatar of games and illusions, known as the Crystal Guardian. (PROSE: The Quantum Archangel)

According to the Sixth Doctor, the Toymaker originated in another universe before this one and was hauled into the Doctor's universe by some kind of catastrophe. Because of this, the usual laws of physics don't apply to him. The Toymaker himself stated that while in the beginnings of the universe he used his powers for other things, he eventually got bored of thousands of millennia of pointless creation and pointless destruction, and found a new source of amusement - games. (AUDIO: The Nightmare Fair)