Stenza

The Stenza were a warrior race and self-proclaimed conquerors of the Nine Systems. Relative to Earth, they had cold skin and could kill humans by placing their hands to the face and freezing them to death.

They would then take a tooth from their victims as a trophy, and graft it onto their faces. According to the Doctor's analysis of one of their transport pods, they came from 5,000 galaxies away from Earth and the Milky Way.

In order to decide who would become the next leader of the Stenza, an individual would be given a selected "trophy" to hunt and capture without the use of weapons or assistance. One Stenza called Tzim-Sha travelled to Earth in order to capture his selected trophy, Karl Wright, so he could become the leader of the Stenza. (TV: The Woman Who Fell to Earth)