Azathoth (All-Consuming Fire)

Azathoth or Azazoth was the alias taken on by a slug-like creature that was imprisoned on the planet of Ry'leh. It used its hypnotic powers to control its followers and converted those followers into Rakshassi. The Seventh Doctor decried it as a mockery of the genuine Azathoth, making a living by usurping the reputation of the Great Old One of the same name. It and its followers died in a fire when the temporal rift connecting Ry'leh to Earth was diverted by the Doctor to San Francisco in 1906, on the date of a great earthquake. (PROSE: All-Consuming Fire, AUDIO: All-Consuming Fire)

Behind the scenes

 * Azathoth originated in the writings of H. P. Lovecraft where it is the greatest of the Great Old Ones, inconceivably huge and powerful entities who act on a vast cosmic scale and exist outside of our universe (sometimes interacting with it to catastrophic effect). Azathoth in particular is the most monstrous and powerful, a mindless demiurge eternally dreaming at the centre of the Universe, which is in itself its own dream. His awakening is a cosmic-level event, heralding the end of all things.
 * The name was changed to Azazoth for the audio adaptation of All-Consuming Fire.