The "Cave Creature" (real name unknown) is a strange telepathic predator found in (but not actually native to) the planet Setarus, which is located in the mysterious "Divergent Universe" visited by the Eighth Doctor and Charley Pollard. Its origins remain unknown.
This organism appears like an enormous cave system, but is actually alive. The walls of the cave absorb nutrients and the streams act like a circulatory system. It uses its telepathic abilities to lure prey into it and probe the minds of its victims to manipulate them by constructing elaborate illusions. As the victims become lost in the Cave Creature's innards, both their physical bodies and their minds are eventually consumed by the beast. However, the consumption of minds might pose a risk to the Cave Creature, as its own alien mentality makes it unable to cope with some of the intense emotions acquired from its victims.
- Big Finish Doctor Who audio stories, "The Twilight Kingdom" (2004)