For Ubbo-Sathla is the source and the end. Before the coming of Zhothaqquah or Yok-Zothoth or Kthulhut from the stars, Ubbo-Sathla dwelt in the steaming fens of the newmade Earth: a mass without head or members, spawning the grey, formless efts of the prime and the grisly prototypes of terrene life … And all earthly life, it is told, shall go back at last through the great circle of time to Ubbo-Sathla.
The Book of Eibon
There, in the grey beginning of Earth, the formless mass that was Ubbo-Sathla reposed amid the slime and the vapors. Headless, without organs or members, it sloughed from its oozy sides, in a slow, ceaseless wave, the amoebic forms that were the archetypes of earthly life. Horrible it was, if there had been aught to apprehend the horror; and loathsome, if there had been any to feel loathing. About it, prone or tilted in the mire, there lay the mighty tablets of star-quarried stone that were writ with the inconceivable wisdom of the pre-mundane gods.
Ubbo-Sathla by Clark Ashton Smith
Ubbo-Sathla is the spawner and source of all earthly life, and may be an earthly manifestation of Shub-Niggurath. It is believed to be the source from which the Elder Things derived Shoggoths, and, either directly or indirectly, the Mi-Go derived protomatter.
It originally existed at the centre of the first continent (Pangaea) which may now be in Antarctica - this was the belief of at least three members of the post-World War II Karotechia who sought the knowledge contained on the tablets it guards before being killed by Delta Green in Operation Southern Hospitality. The high body count of this phase of Southern Hospitality suggests that Ubbo-Sathla may indeed have been encountered. It has been suggested that Ubbo-Sathla's absorbtion of one or more Karotechia members may have inadvertently given rise to the phenomenon of Shoggoths taking human shape, or Shoggoth Lords, when their sorcerously empowered bodies provided Ubbo-Sathla with a human "template".
Apart from visiting Ubbo-Sathla in person, the only known method of gaining the knowledge contained upon the tablets is by using the artefact known as the Crystal of Zon Mezzamalech, which is also fraught with danger. Some other method of scrying might possibly work, but even the perception of Ubbo-Sathla seems to induce a devolutionary effect.