Korst Gogg Thek Lutiven-Day Slitheen

Korst Gogg Thek Lutiven-Day Slitheen was the son of Kist Mag Thay Lutiven-Day Slitheen of the Slitheen family. As part of the plans of the Slitheen to 'turn off' the Sun, he had travelled to the planet Earth with his father. In school had 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. (SJA: 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 other surviving 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. (SJA: The Lost Boy)