Subterranean Exxilon

s, or simply Subterraneans, (PROSE: Death to the Daleks) were a faction of Exxilons that broke away from the main species and fled into the depth of Exxilon. (TV: Death to the Daleks)

History
The Exxilons constructed the Great City of the Exxilons as a monument to their culture. However, the City grew intelligent, drove out its creators and brought down their civilisation. As they regressed, the Exxilons grew fearful of the City and began worshipping it but a break-away group refused to do so and fled underground, hoping to one day bring down the City and break its hold over the rest of their species. (TV: Death to the Daleks) This break-away group became the Subterraneans. (PROSE: Death to the Daleks)

When human and Dalek expeditionary forces came to Exxilon in search of parrinium during the Third Dalek War, (PROSE: The Secret Lives of Monsters) the Exxilon High Priest agreed to help them acquire the mineral if they wiped out the Subterraneans. However, the Third Doctor and Sarah Jane Smith made contact with the Bellal and Gotal of the Subterranean group and agreed to help them defeat the City. Another of their number, Jebal, spied on the parrinium mining site as the City defences attacked the Exxilons and the Daleks.

The Doctor and Bellal ventured into the City and completed the intelligence tests blocking access to the main control room. Together with a successful Dalek attempt to blow up the City's beacon from the outside, the Doctor's interference helped achieve the Subterraneans' mission to destroy it. (TV: Death to the Daleks)