The Voormis are a fictional race of cave-dwelling humanoids who worship Tsathoggua.
The Voormis are the primary focus of a "posthumous collaboration" short story by Lin Carter after Clark Ashton Smith's death, The Scroll of Morloc (First published in 1976, The Year's Best Fantasy Stories: 2, and again in 1980 in Lost Worlds). They are referred to as the Voormi (plural: Voormis) in the fictional manuscript The Pnakotic Fragments. The Voormis considered themselves the chosen minions of Tsathoggua, and his direct descendants.
...for it was commonly believed that their supreme pontiff and common ancestor had been fathered by none other than Tsathoggua himself during a transient liaison with a minor female divinity who rejoiced in the name of Shathak
— Lin Carter and Clark Ashton Smith, "The Scroll of Morloc"
Now the Voormis had, from their remotest origins, considered themselves the chosen minions of Tsathoggua, the sole deity whose worship they celebrated. And Tsathoggua was an earth elemental ranged in perpetual and unrelenting enmity against the Rhan-Tegoth and all his kind, who were commonly accounted elementals of the air, and were objects of contempt to those of the Old Ones, like Tsathoggua, who abominated the airy emptiness above the world and by preference wallowed in darksome and subterranean lairs.
— Lin Carter and Clark Ashton Smith, "The Scroll of Morloc"
The Voormis are described as three-toed, umber-colored, fur-covered humanoids though they are carefully differentiated from their traditional enemies (the shaggier-haired but superficially similar Gnophkehs who worshiped the Great Old One Rhan-Tegoth). Both of them are further differentiated from true humans. The Voormis communicate by dog-like howls.
They reside in the continent of Hyperborea, which will be known in the future as Mhu Thulan. The Voormi inhabit cave systems under the four-coned extinct volcano named after them - Mount Voormithadreth, the tallest peak in the Eiglophian mountains. Their ancestors, as described by Carter's narrative, were originally thralls of the Serpent-people who escaped after the continent of the latter sank to the sea. They are shamanistic and apparently begun dwelling underground in an effort to imitate their deity, Tsathoggua, under the leadership of the eponymous Voorm.