Colony Sarff
Colony Sarff was a servant to Davros comprised of several snake-like creatures. Although acting as an individual, the snakes were able to act independently, but made decisions as a democracy.
Sarff searched for the Doctor, travelling to the Maldovarium, the Shadow Proclamation, and Karn where he encountered the Sisterhood of Karn who could stop him from using his powers against them. Whilst unkowingly in the presence of the Doctor, he told Ohila, the Sisterhood's High Priestess, that Davros was searching for the him.
Sarff returned to Davros, who told him that in order to find the Time Lord he must first find his friends. He then followed Clara Oswald and Missy to Essex in 1138, where one of the snakes attacked Bors. He transferred the Doctor, Clara, and Missy (with their hands bound by more snakes) to his spaceship where they travelled to Skaro. He then accompanied the Doctor to see Davros, who asked him to leave. (TV: The Magician's Apprentice)