Men knew him as the Dweller in Darkness, that brother of the Old Ones called Nyogtha, the Thing that should not be. He can be summoned to Earth's surface through certain secret caverns and fissures, and sorcerers have seen him in Syria and below the black tower of Leng; from the Thang Grotto of Tartary he has come ravening to bring terror and destruction among the pavilions of the great Khan. Only by the looped cross, by the Vach-Viraj incantation and by the Tikkoun elixir may he be driven back to the nighted caverns of hidden foulness where he dwelleth.
—Henry Kuttner, "The Salem Horror"
Nyogtha (the Thing That Should Not Be) appears in Henry Kuttner's short story "The Salem Horror" (1937). According to the story, the Necronomicon refers to Nyogtha as "the Dweller in Darkness"--an epithet used by August Derleth in the story of the same name to refer to Nyarlathotep; thus, it may be that Nyogtha is yet another of Nyarlathotep's nigh-endless avatars. Nyogtha appears as a shapeless, dark mass.
In his short story "Path of Corruption," Steve Berman has a group of New Orleans-based hustlers worshipping Nyogtha.
In the 1965 horror film Dark Intruder Nyogtha is mentioned towards the end, along with Sumerian Goetic demons such as Astaroth and Asmodeus.
Read more about this topic: Henry Kuttner Deities