Lovecraft referenced Yuggoth in the 1929-1930 poetry cycle Fungi From Yuggoth. Yuggoth is described in "Recognition", the ninth sonnet in the series: The novella The Whisperer in Darkness, written in 1930 and published in 1931, Lovecraft develops the Yuggoth concept in greater detail, as the origin of strange beings who secretly inhabit isolated mountains in Vermont.
Yuggoth... is a strange dark orb at the very rim of our solar system... There are mighty cities on Yuggoth—great tiers of terraced towers built of black stone... The sun shines there no brighter than a star, but the beings need no light. They have other subtler senses, and put no windows in their great houses and temples... The black rivers of pitch that flow under those mysterious cyclopean bridges—things built by some elder race extinct and forgotten before the beings came to Yuggoth from the ultimate voids—ought to be enough to make any man a Dante or Poe if he can keep sane long enough to tell what he has seen...
Yuggoth is the planet where the extraterrestrialMi-go have established a colony. The Mi-go's city sits at the edge of a pit wherein dwells an ancient and horrifying entity feared by the Mi-Go. They periodically abandon the city on those occasions when it rises from the pit and can be seen directly. The being Cxaxukluth, along with Tsathoggua and his parents, migrated to Yuggoth from Xoth. A dysfunctional family in their own right, Cxaxukluth's progeny abandoned their patriarch and sought refuge deep in the bowels of Yuggoth, owing to Cxaxukluth's cannibalistic tendencies. Soon thereafter they fled Yuggoth, though Cxaxukluth still dwells there to this day.
It came to the earth from lead-grey Yuggoth, where the cities are under the warm, deep sea. —H. P. Lovecraft, "The Horror in the Museum"
On Yuggoth, the Mi-go mine a strange metal known as tok'l. Tok'l-metal is used in the manufacture of the Mi-go's notorious "brain cylinders", but it has other ritual uses as well.
In other fiction
Yuggoth itself hung directly overhead, obscenely bloated and oblate, its surface filling the heavens... and all the time pulsing, pulsing, pulsing like an atrocious heart, throbbing, throbbing.
—Richard A. Lupoff, "The Discovery of the Ghooric Zone—March 15, 2337"
In Richard A. Lupoff's 1977 short story "The Discovery of the Ghooric Zone—March 15, 2337", Yuggoth is the hypothetical Planet X or Planet Nine—then predicted by perturbations to Neptune and Pluto's orbits, and now, in 2017, by the orbit of several trans-Neptunian objects. Lupoff's Yuggoth is a colossal planet, double the size of Jupiter and as big as 600 Earths. The planet pulses, throbs, and glows with a "low crimson radiance" from pulsating lava tectonics, "like an atrocious heart." Its rotational velocity is 80,000 kilometers per hour, and thus Yuggoth is oblate and flattened at the poles. The planet has numerous moons like the other giant bodies of our outer solar system, to include the single moons Nithon and Zaman, and the twin-moons Thog and Thok—all names intertextually chosen by the Lovecraft enthusiast on board the planet's visiting ship Khons, a character named "Sri Gomati," from Lovecraft's long sonnet sequence, "Fungi from Yuggoth".
Other references
Yuggoth is briefly mentioned in John Bellairs's The Face in the Frost as part of a wizard's model of the cosmos. It is described as "the terrible black planet... which rolls aimlessly in the stupefying darkness."
A being or "living concept" which is dubbed a Yuggoth by the narrator possesses Allan Quatermain's abandoned mortal shell in the illustrated story Allan and the Sundered Veil in the first graphic novel volume of The League of Extraordinary Gentlemen. The Yuggoth is described as being known as "a creature, a planet, and an idea" and is an abstract alter-dimensional entity which is entering through the hole in the fabric of time that the story revolves around.
An entity referred to as both Nyarlathotep and "Yuggoth's emissary" appears towards the end of . The being is involved in diplomacy in the Blazing World.
Yuggoth is also a theme which is discussed in detail in Kenneth Grant's Typhonian Trilogy.
The H. P. Lovecraft story The Whisperer in Darkness is the main focal point in the Electric Wizard song "Weird Tales: Electric Frost/Golgatha/Altar of Melektaus." This can be seen in lyrics such as "From ancient Yuggoth, black rays emit, Evil's narcotic cyclopean pits."
Jack Chalker's novel Horrors of the Dancing Gods references "Far Yuggoth" as the continent of the sub-Earth world of Husaquahr from which all evil things come. Far Yuggoth can only be reached by taking a ship called the Hovecraft.
In Brian Keene's novel A Gathering of Crows, Levi traps the minions of Meeble by tricking them into the Labyrinth, a corridor between planes of reality. When his adversaries close in to seemingly finish him, he informs that they are powerless. As they are now on Yuggoth, which is the planet ruled by Behemoth, a more powerful member of the Thirteen...
In the video game Phoenix Point, one of the backgroundshort stories identifies Yuggoth as the source of an infestation that wiped out an ancient civilization millions of years ago. Presumably, the similar infestation threatening Earth in the game comes from the same source.
In Edgar Cantero's novel Meddling Kids Yuggoth makes a brief appearance in the climax.
Caitlín R. Kiernan's 2017 novella, Agents of Dreamland, involves the New Horizons probe being sighted by the inhabitants of Yuggoth during its 2015 flyby of Pluto.
Moons
Nithon
Nithon is a cloud-laden moon of Yuggoth. It is covered by fungi and has luminescent clouds that block all sunlight.
Thog and Thok
Thog and Thok are twin moons of Yuggoth. Very little is known about these moons, though Thog is said to be a pitch-black world. On the surface of Thok is the fabled Ghooric Zone—a green-litten cavern containing a putrid lake where "puffed shoggoths splash".
Links with Pluto
When Pluto was discovered in 1930, Lovecraft himself very casually suggested, in a letter to his friend James F. Morton, dated on 15 March 1930 that Yuggoth might "probably" be the same as Pluto. Other writers have since claimed that Yuggoth is actually an enormous trans-Neptunian world that orbits perpendicular to the ecliptic of the solar system. The Italian astronomer Albino Carbognani has suggested that any planet discovered beyond Pluto might be named Yuggoth.
