The entity created as the product of the Darlusian Zhth when it inhabited the form of a Dron. Zee retained all of the knowledge and memories the Doctor had prior to his Retrocyclic Regeneration and used this knowledge to mentor of the Young Doctor, quickly becoming a constant companion and the Young Doctor’s trusted friend and ally; the first after his regeneration. He bestowed the name, ‘11.1’ on the Doctor soon after his Retrocyclic regeneration when the Young Doctor refused to answer to the name ‘Doctor’ because he had lost his memory.