Abholos (Devourer in the Mist) a great grey, festering glob of endless malevolence.
There are two theories about the creation of Abholos, in both case he is a byproduct.
Although not confirmed, he is said to be a side effect from the mating of Ghisguth and Zstylzhemghi, which gave birth to Tsathoggua. Abholos in this case is the lesser brother or cousin and more like a self-willed placenta taken form.
Another explination for Abholos is that he is a spawn of Cthulhu, born from his bile and tears.