Cthulhu is a character extracted from the literature of H.P. Lovecraft. Lovecraft formed, in some of his stories, a mythology of horror based on the existence of parallel universes and beings from them - among which is Cthulhu - that existed "before time", and whose contact with humans has terrible consequences . Within their stories, the theme is primordial chaos, and Lovecraft introduces the notion that everything we know makes sense only within our space-time; When an event that breaks with spacetime happens, madness begins.

Within this cosmology, known as the Myths of Cthulhu, Cthulhu is an emblem, central character and one of the recurring figures: although it is not the most powerful, it is the most popular of all these beings, and plays a central role in the story The call of Cthulhu.

Cthulhu is an extraterrestrial creature whose physical characteristics and abilities make him something like a god to humans. His main followers and servants are the star seed of Cthulhu. In the novel In the mountains of madness, small suckers of Cthulhu were at war with several races in a distant past, on planet Earth. He is also worshiped by most of the Deep Ones, half human beings half batrachian, who inhabit the oceans. Above the Ancient Ones are the Outer Gods, although the universe of Lovecraft does not lend itself too much to the hierarchical steps. According to his human followers, Cthulhu is the high priest of these beings.

It is described - precisely in the story Cthulhu's Call - as a huge creature comparable to a moving mountain, with the head of an octopus or squid, and a bloated dragon body, with their respective rudimentary wings. It has the ability to alter its shape, although it is always basically the same. Its scaly body is composed of a substance different from those found on our planet, a kind of gelatinous mass that makes it practically indestructible. Anyway, even if his physical body is completely destroyed (very improbable thing), his extraterrestrial nature would re-form him in hours. He was one of the conquerors of the Earth and dominated from the depths of the ocean.

According to mythology, Cthulhu lies dreaming under a seal in the submerged city of R'lyeh (somewhere in the Pacific Ocean). He hopes to escape some day (the day when "The stars are back in position") with the help of cultists and sectarians to re-extend his power on Earth. To him they dedicate the psalm "Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn" which roughly means "In the City of R'lyeh, the late Cthulhu, awaits dreaming".