Great Race of Yith
The Great Race of Yith are aliens in the Cthulhu Mythos of H. P. Lovecraft. They first appeared in Lovecraft's short story "The Shadow Out of Time" (1936). They are called the Great Race because they are the only beings to have mastered time travel. Throughout "The Shadow Out of Time" they are simply referred to as "The Great Race" whilst their planet's name is only mentioned once.
The Great Race in the mythos 
[T]he Great Race ... waxed well-nigh omniscient, and turned to the task of setting up exchanges with the minds of other planets, and of exploring their pasts and futures. It sought likewise to fathom the past years and origin of that black, aeon-dead orb in far space whence its own mental heritage had come – for the mind of the Great Race was older than its bodily form. . . The beings of a dying elder world, wise with the ultimate secrets, had looked ahead for a new world and species wherein they might have long life; and had sent their minds en masse into that future race best adapted to house them – the cone-shaped beings that peopled our earth a billion years ago.—H. P. Lovecraft, "The Shadow Out of Time"
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, whom they initially subdued. However, this enemy over time increased in number and near the close of the Cretaceous era (about 65 million years ago), rose up and finally destroyed the civilisation of the Race of Yith, forcing the Yithians to flee en masse to other bodies located far in the future.
In the bodies that the Great Race of Yith inhabited on the Earth, they were tall and cone-shaped, rising to a point with four strange appendages, all of which can extend and recede at will to any distance up to about ten feet. Two terminate in claws, the clicking of which acted as a method of communication, a third in four red "trumpets," and the fourth, a yellowish globe featuring three eyes around the central circumference, flower-like ears on top and tentacles on the underside. They have no sexes and reproduce by spores instead, though rarely because of their species longevity. Movement is achieved via expansion and contraction of a grey, rubbery layer at the base of the conical body.
The unique ability of this scientifically advanced race was 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 cases with books, made of an incredibly long-lasting material, 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) from the past and future. 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 or suppressing all knowledge of the Great Race. Even so, it is possible for scraps of knowledge or experiences gained from their time with the Great Race to remain in dreams.
In the short story "The Challengers From Beyond", H. P. Lovecraft describes a race of grey worm/centipede-like, creatures (Yekubbians) which have similar abilities to the Great Race of Yith, but without the power of time travel by mind transfer. They use an odd hieroglyph-engraved cube to send out into the cosmos and, once landed on a planet, it is activated by biological interaction and light. This then engages the life form in a similar process to the Yithian's mind transfer. One of these cubes is what apparently landed on the earth during the reign of the Great Race and transferred some of their minds. It was therefore stored away so it couldn't affect them again, but not destroyed as the technology was new to them. This was later "translated" by a man and resulted in the Eltdown Shards.
Coleopterous race 
Because the Great Race traveled 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.
Any creature which is possessed by the Great Race of Yith has the host's mind transferred to the original Yithian's body. Because of this, when the Great Race of Yith felt obliged to transfer their minds to the 'beetle folk' due to their defeat against the flying polyps, the people who originally possessed the bodies of the Coleopterous race would presumably have been destroyed by the victorious polyps.
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.
The Great Race in popular culture 
- Contemporary and correspondent of H.P. Lovecraft, Duane W. Rimel penned a poetry cycle called "Dreams of Yith" which was published in The Fantasy Fan for July and Sept 1934. The cycle was revised by Lovecraft, by Clark Ashton Smith and also by Robert H. Barlow. Dreams of Yith can be found in August Derleth's anthology Dark of the Moon: Poems of Fantasy and the Macabre.
- In the Futurama episode "A Bicyclops Built for Two", a creature resembling a purple Yithian 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 by writer/director Joseph Nanni, a Yithian named Gary Gribstock auditions for a role in a film inspired by H.P. Lovecraft
- Harms, Daniel (1998). "Great Race of Yith". The Encyclopedia Cthulhiana (2nd ed. ed.). Oakland, CA: Chaosium. pp. 128–30. ISBN 1-56882-119-0.
- —"Pnakotic Manuscripts", pp. 242–3. Ibid.
- —"Pnakotus", p. 243. Ibid.
- Lovecraft, Howard P. (1982) . "The Shadow Out of Time". The Best of H. P. Lovecraft: Bloodcurdling Tales of Horror and the Macabre (1st edition ed.). Ballantine Books. ISBN 0-345-35080-4.
- Perhaps these entities had come to prefer earth's inner abysses to the variable, storm-ravaged surface, since light meant nothing to them. Perhaps, too, they were slowly weakening with the aeons. Indeed, it was known that they would be quite dead in the time of the post-human beetle race which the fleeing minds would tenant. -The Shadow Out of Time.