Kythanil (also Kythamil) - double planet that once revolved around the star Arcturus. Tsathoggua's followers, the Voormi , once lived here, and Zvilpogghua's “daughter,” Sfatlicllp, may also have dwelt here. The planet was destroyed in some catastrophe, but not before the Voormis moved to primal Hyperborea.
Ariel Prescott, in her Visions from Yaddith, implies that the planet Kythamil is still in existence in 1927, although Kythanil was destroyed millions of years before the first homanids.
H. P. Lovecraft created Kythanil and it was taken up by Lin Carter.