The Stenza are a warrior race and self-proclaimed conquerors of the Nine Systems. In order to become the race’s next leader, the Stenza must travel 5000 galaxies to planet Earth and hunt their selected human trophy in a ritual they call ‘The Ritual of the Stenza’. The Stenza have very cold skin and can kill humans with a touch of their hands, freezing them to death.
A Stenza warrior known as T’zim-Sha (or Tim Shaw as the Doctor called him) came to Sheffield to locate and kill his selected target, Karl Wright. He arrived to Earth in a transport pod. Like his skin, this too was cold to the touch. He also arrived with a Gathering Coil, half-organic and half-machine, which he used to help locate his trophy. Beneath his removable face plate, dozens of teeth were grafted to his face; each tooth taken from a victim, representing a conquest.
His ritual came to an abrupt end when he met the Doctor, Ryan, Graham and Yaz. The Doctor offered him a chance to change, but he didn’t take it and was sent back to his home planet, leaving Karl alive.