Template:Planet Avalon was a planet similar to Earth, however, contained mythological creatures from the ancient stories of Merlin and Arthur Pendragon. The First Doctor, Susan Foreman, Ian Chesterton and Barbara Wright arrived there once and met up with all kinds of species, including Wizards and Dragons.
The planet was located by the Human Empire of the 30th Century and they attacked the planet and its local inhabitants in order to gain the Merlin's Helm for the use of tremendous power. However, Nanobots restrained the arrival of outsiders and so their ships burned up in the atmosphere.
The planet was actually controlled by the Cephiles, who were god-like creatures who protected the way that Avalonian nature progressed. They were forced to die after the Siege of Fluxford. (The Sorcerer's Apprentice)