- "If that abyss and what it held were real, there is no hope. Then, all too truly, there lies upon this world of man a mocking and incredible shadow out of time."
- ―Nathaniel Wingate Peaslee
The Great Race of Yith are a sapient species originating from the dead planet Yith. They are called the Great Race because they are the only beings to have mastered time travel.
The Great Race are beings of enormous intellectual and psychic powers that once dwelt on the dying world of Yith. They escaped the destruction of their home planet by transferring their minds to the bodies of a species native to the Earth in the far distant past. They lived on this planet for 200 million years or so, in fierce competition with the Flying Polyps, until this enemy finally destroyed their civilization near the close of the Cretaceous era (about 65 million years ago).
In the bodies they inhabited on the Earth, they were tall and cone-shaped, rising to a point with four strange appendages – two terminating in claws, a third in a "trumpet", and the fourth, a yellow globe which functioned as a sensory organ. They have no genders and reproduce by spores instead. The unique ability of this scientifically-advanced race is to travel through time by swapping minds with creatures of another era. This allowed them to satisfy their interest in Human culture, science, and occult beliefs. Occupied beings' minds transferred to Yithian bodies against their will; these "captive minds" were queried by skilled inquisitors while the Yithians using their bodies learned as much as possible about the societies in which they dwelt.
Although captive minds were prisoners, they were nonetheless granted some freedoms in exchange for their cooperation. Those captive minds who cooperated with the Great Race were allowed to wander the Yithian cities at will and to browse the Yithians' gigantic library, which contained metallic tubes with scrolls that recorded the histories of uncounted alien races, including humanity. Creatures inside a Yithian body could also communicate with other captive minds from across our universe (and beyond). Once the Great Race had learned all they could from a captive mind, the occupied being's intellect was swapped back, with the additional precaution of erasing all knowledge of the Great Race.
Because the Great Race travelled to the future as well as the past, they foresaw their own destruction by the Flying Polyps. Before the fateful day, the Great Race transferred their best minds forward through time into the bodies of the "beetle folk" (the coleopterous race), Earth's dominant species after humankind. One of the factors involved may have been the fact that the Flying Polyps are completely gone by this point in time.
The Lost City of Pnakotus (also called the Library City, the Lost City of the Archives and Pnakotis) is located in Australia's Great Sandy Desert. This primordial city is where the Great Race housed their enormous library.
The library of Pnakotus held the Pnakotic Manuscripts, a legendary tome containing a detailed chronicle of the Great Race's history, among other things. Copies of this manuscript would later be passed down through the ages, eventually falling into the hands of sinister cults which would guard them into modern times.
- This species first appeared in H. P. Lovecraft's story "The Shadow Out of Time" (1936). Throughout the story, they are simply referred to as "the Great Race" whilst their planet's name is only mentioned once.
- In the Futurama episode "A Bicyclops Built for Two", a creature resembling a purple Yithian host (only much smaller in size) can be seen as a would-be bride.
- In the computer game Call of Cthulhu: Dark Corners of the Earth, the Great Race and its advanced technology play an important part in the story, and appear in the very end of the game. Their purpose in the game is expanded to a greater level of detail if the player is able to attain an "A" as his final score.
- The Darkest of the Hillside Thickets released an album based on "The Shadow Out of Time" called "The Shadow Out of Tim" which naturally features the Yithians.
- German heavy metal band Rage have done 2 songs featuring the Great Race, both appearing on their 1995 album Black in Mind. The 2 songs are titled "Shadow Out of Time" and "In a Nameless Time".
- In The 4400 episode "Wake Up Call," Tess Doerner bases her description of the future on the city of the Great Race as described in "The Shadow Out of Time."
- In May 2006, special tournaments were held for the Call of Cthulhu Collectible Card Game where the winners were pitted against a special, overpowered deck featuring the Yithians as played by the tournament organizer.
- In "To Mars and Providence", the Martians from The War of the Worlds are given the psychic attributes of the Great Race.
- In the short film Casting Call of Cthulhu, a Yithian named Gary Gribstock auditions for a role in a film inspired by H.P. Lovecraft