Tsathoggua (the Sleeper of N'kai, also known as Zhothaqquah) is a supernatural entity in the Cthulhu Mythos shared fictional universe.

[2] His first appearance in print, however, was in Robert E. Howard's story "The Children of the Night", written in 1930 and published in the April–May 1931 issue of Weird Tales.

His next appearance in print was in H. P. Lovecraft's story "The Whisperer in Darkness", written in 1930 and published in the August 1931 issue of Weird Tales.

The first description of Tsathoggua occurs in "The Tale of Satampra Zeiros", in which the protagonists encounter one of the entity's idols: He was very squat and pot-bellied, his head was more like a monstrous toad than a deity, and his whole body was covered with an imitation of short fur, giving somehow a vague sensation of both the bat and the sloth.

He will rise not from his place, even in the ravening of hunger, but will wait in divine slothfulness for the sacrifice.Robert M. Price notes that "Lovecraft's Tsathoggua and Smith's differ at practically every point".

Lovecraft, dropping Smith's bat and sloth comparisons, refers to the entity in "The Whisperer in Darkness" as the "amorphous, toad-like god-creature mentioned in the Pnakotic Manuscripts and the Necronomicon and the Commoriom myth-cycle preserved by the Atlantean high-priest Klarkash-Ton"[4] (the priest's name was Lovecraft's nickname for Tsathoggua's creator, Clark Ashton Smith).

The basin ... was filled with a sort of viscous and semi-liquescent substance, quite opaque and of a sooty color.... [T]he center swelled as if with the action of some powerful yeast [and] an uncouth amorphous head with dull and bulging eyes arose gradually on an ever-lengthening neck ... Then two arms—if one could call them arms—likewise arose inch by inch, and we saw that the thing was not ... a creature immersed in the liquid, but that the liquid itself had put forth this hideous neck and head, and [it was now forming arms] that groped toward us with tentacle-like appendages in lieu of claws or hands!

... Then the whole mass of the dark fluid began to rise [and] poured over the rim of the basin like a torrent of black quicksilver, taking as it reached the floor an undulant ophidian form which immediately developed more than a dozen short legs.

The Call of Cthulhu roleplaying game's entry on Formless Spawn also claims that they are powerfully acidic in substance and can dissolve human flesh with even a slight touch.

In "The Mound" the people of the subterranean world of K'N-Yan had once worshipped Tsathoggua until a scientific expedition exploring N'Kai encountered the Formless Spawn.

The Voormis are described as three-toed, umber-colored, fur-covered humanoids[8] though they are carefully differentiated from their traditional enemies (the shaggier-haired but superficially similar Gnophkehs who worshiped the Great Old One Rhan-Tegoth).

They reside in a continent in Hyperborea which will be known in the future as Mhu Thulan: specifically in cave systems under the four-coned extinct volcano named after them—Mount Voormithadreth, the tallest peak in the Eiglophian mountains.

They are shamanistic and apparently began dwelling underground in an effort to imitate their deity, Tsathoggua, under the leadership of the eponymous Voorm.

[13] According to Smith's "Parchments of Pnom", Tsathoggua is the spawn of Ghisguth and Zystulzhemgni, as well as being the mate of Shathak and the parent of Zvilpogghua.

In Kevin L. O'Brien's "October Surprise" (2006) Hziulquoigmnzhah's mate is Zstylzhemghi's sister Klosmiebhyx who bore him two entities likely matching with the Welsh giant Ysbaddaden and the Scottish war-goddess Scáthach,[15] since both named after these two demigods.

[citation needed] Athammaus tried to execute him by beheading, but because of his preternatural heritage, such attempts proved unsuccessful and only served to aggravate him.

He usually takes the form of an armless, winged, bipedal toad with a long, rubbery neck and a face completely covered in tentacles.