Korst Gogg Thek Lutiven-Day Slitheen was a young member of the Slitheen family. He was the twelve-year-old son of Kist Magg Thek Lutiven-Day Slitheen and the nephew of Glune Fex Fize Sharlaveer-Slam Slitheen.
As part of the plans of the Slitheen to "turn off" the Sun, Korst had travelled to the planet Earth with his father and uncle. In school, he posed as a fat, unpopular boy named Carl. When Sarah Jane Smith intervened, Korst teleported away as the machine failed, killing the rest of his family. (TV: Revenge of the Slitheen)
Korst later re-appeared, disguised as Nathan Goss, a child prodigy involved in the Pharos Institute's experiments with the telekinesis amplification device, MITRE. He allied himself with Dax Fex Fize and Bloorm Vungah Bart Slitheen as well as Mr Smith, who secretly worked towards world domination by the Xylok. He sought revenge on Sarah Jane Smith for the death of his family and was involved in the kidnapping of Luke Smith. Mr Smith double-crossed the Slitheen and planned to destroy the Earth, by using Luke's telekinetic power to bring the Moon crashing into Earth. The Xylok was stopped and the three Slitheen left Earth in peace. (TV: The Lost Boy)