Krennos

Krennos was a living planet and the location of Leisureworld, which was built to sap vitality from their customers and feet it to the planet to keep it dormant while being studied.

After being forced to leave Earth in 1966 by the Second Doctor and return to their home planet, (TV: The Faceless Ones) the Chameleons shortly passed Krennos and began to kidnap and impersonate visiting humanoids.

The Sixth Doctor, Crystal, Jason, and Zog visited the planet, and the Doctor was able to communicate telepathically with Krennos to some effect, before defeating the Chameleons once again. (PROSE: Face Value)