In the Conrad & Kirowan stories of Robert E. Howard Koth is referred to as a black cyclopean city. (CIRCLE: "Dig Me No Grave" [Robert E. Howard]) In Conan the barbarian's world, Koth is an ancient Hyborian kingdom. (CIRCLE: "The Hyborian Age" Robert E. Howard) The city of Koth could reside in this kingdom or be a remnant of it.
Koth is also quoted like an Great Old One with Cthulhu and Yog-Sothoth. (CIRCLE: "The Fire of Asshurbanipal" [Robert E. Howard]) Some sources also refer to a creature or possibly Great Old One named Koth. (EXP: "The Lords of Pain" [R. L. Tierney])