Planet (The Extortioner)

An Earth-like planet was used by the Extortioner as his secret base, which was located inside an active volcano. When the Second Doctor arrived on the planet and explored the volcano (leaving John and Gillian in the TARDIS), the Extortioner captured him to keep him from interfering with his plans. The Doctor escaped, caused the volcano to erupt, and tricked the Extortioner into falling to his death. (COMIC: The Extortioner)