The Elemental

The nameless elemental being first appeared in the Doctor's life as a mysterious presence aboard an abandoned spacecraft. Subsequently, it possessed and used the Doctor's TARDIS for its own purposes.

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The Doctor and his hapless passenger Maxwell Edison found a derelict alien ship approaching Earth. Edison sensed a presence, which they saw. The Doctor falsely believed they had seen the last of it. (DWM: Stars Fell on Stockbridge)

Actually, the entity held onto the TARDIS and, after Maxwell had left, directly attacked the Doctor. Now having total control of the TARDIS. The TARDIS shook off the presence and stranded it in early Human history, where savage tribes worshipped it. The Time Lords of Gallifrey, in particular, Tubal Cain, took notice and held the Doctor responsible to negligently allowing the being to interfere with history. Shayde, an ally of the Doctor's, forced the elemental into the Matrix where it could exercise its whims without doing harm in the physical universe. (DWM: The Stockbridge Horror)