Metebelis III

File:St--3z25metebelisiii.jpg The Great One towers over the Third Doctor, in a scene from Planet of the Spiders.

Metebelis III is a planet inhabited by giant, intelligent spiders, including The Great One, seen in the Third Doctor story Planet of the Spiders. The Doctor's encounter with the Great One in her cave of crystals on Metebelis III led to radiation poisoning which led to his regeneration into the Fourth Doctor.