Terilepitil-They are a reptilian humanoid species, they cannot survive long without breathing soliton gas, which is highly combustible when combined with oxygen. As an advanced society, they enjoy a heightened appreciation of both aesthetics and warfare, and have been known to employ bejeweled androids. Criminal punishment in Terileptil society includes life imprisonment working in tinclavic mines on the planet Raaga, often with sub-standard medical care.
In 1666, a group of Terileptil prison escapees hidden near London attempted to use a genetically enhanced version of the Black Plague to destroy humanity. The destruction of their lab in Pudding Lane — with help from the Doctor — causes the Great Fire of London.