Ubbo-Sathla was created by Clark Ashton Smith in "Ubbo-Sathla" (1933). Described as a formless, protoplasmic mass, it is said to be the ultimate progenitor from which all life on Earth descended.
It possesses no will or purpose beyond a blind generative force, and is said to guard lost tablets of primordial wisdom. Those who seek it risk having their consciousness dragged back into the mindless beginning of all things.