Ghatanothoa, the Lord of the Volcano, is a Great Old One and the first born of Cthulhu. It is a huge, amorphous monstrosity which is so hideous, anyone who gazes upon it (or even a perfect replica) is petrified into a living mummy. The victim is permanently immobilized, the body taking on the consistency of leather and the internal organs and brain preserved indefinitely, yet remains fully aware. Only the destruction of the subject's brain can free it from its hellish prison, though the unfortunate is likely to be incurably insane long before the welcomed release.
Ghatanothoa is currently trapped underneath Mount Yaddith-Gho in sunken Mu. He was brought to Earth from the planet Yuggoth by an ancient, alien race, possibly the Mi-go, who built a colossal fortress atop Yaddith-Gho and sealed Ghatanothoa inside the mountain beneath a large trapdoor. Ghatanothoa was worshipped by the ancient Muvians, who both feared and respected him because of his ability to turn any humans that beheld him into living, thinking mummies.