Azathoth

"Outside the ordered universe that amorphous blight of nethermost confusion which blasphemes and bubbles at the center of all infinity—the boundless daemon sultan Azathoth, whose name no lips dare speak aloud, and who gnaws hungrily in inconceivable, unlighted chambers beyond time and space amidst the muffled, maddening beating of vile drums and the thin monotonous whine of accursed flutes."

- The Dream-Quest of Unknown Kadath

Azathoth is regarded as the ruler of the Outer Gods: an eldritch, primordial and chaotic entity which created the universe and resides at the center of his creation, where he sleeps and dreams to the music of his flute-playing idiot alien servitors and eternal drums.

Azathoth spawned three children: Nyarlathotep, the Nameless Mist and Darkness. Through the Nameless Mist, he has a grandson called Yog-Sothoth; and through Darkness a granddaughter called Shub-Niggurath. His descendants may include many or all of the Great Old Ones, such as Cthulhu and Tsathoggua; which in turn have produced numerous descendants among the lesser races.

Biology
Before his mysterious exile, Azathoth's original form was that of a bivalvular shell supported by multiple pairs of flexible legs. The interior of the shell contained "several jointed cylinders, tipped with polypous appendages" and a "horrible bestial, mouthless face, with deep-sunk eyes and covered with glistening black hair". His current form is even more monstrous.

Cultural significance
Azathoth is worshiped by numerous space-faring species, such as the enigmatic Mi-Go and the insectoid Shans; the latter which are noted for the atrocious brutalities committed by the members of Azathoth's church.