Also known as Tannis, a hidden Time Lord and antithesis to the other Time Lords/Gods of the Fourth

Killed by The Doctor during death comes to time

Motivation:
Tired of never being allowed to use his powers, Tannis sets about conquering the universe without the use of the Power as both a distraction to the other Time Lords and a method to entice them to become empathic to the mortals, get involved and use the Power themselves (thus condemning them to exile or death from the other Time Lords). His intent is to get rid of all Time Lords, enabling him to use the Power at will after they've gone.

Presumably the Gods of the Fourth metioned in the minister of chance other than the minister were not in the same universe/dimension/World as Tannis at the time of death comes to time and therefore as exiles/hermits would not care what happened or interfere in his plans.

Ergo Kitty is probably from the dimension Tannis comes from as the non-Earth humanoids she spends time with have evolved for lower gravities.