Caesofine gas

Sezerfine gas was a type of gas utilised by the Sontarans as a Clone feed. In preparation of their 2009 invasion atempt of Earth they manipulated humans to utilise ATMOS devices, seemingly a device to neutralise carbon dioxide emissions. However the true purpose of the ATMOS devices was to release Sezerfine gas into the Atmosphere and thus turn the Earth into a Cloning World. (DW: The Sontaran Stratagem / The Poison Sky; SJA: The Last Sontaran)