Cthulhu is a fictional cosmic entity created by horror author H. P. Lovecraft in 1926, first appearing in the short story "The Call of Cthulhu" when it was published in Weird Tales in 1928. He is a Great Old One of great power who lies in a death-like slumber beneath the Pacific Ocean in his sunken city of R'lyeh. He remains a dominant presence in the eldritch dealings on Lovecraft's world.
Cthulhu is one of the central Great Old Ones and their high priest of the Lovecraft Mythos. It is often cited for the extreme descriptions given of its hideous appearance, its gargantuan size, and the abject terror that it evokes. Cthulhu is often referred to in science fiction and fantasy circles as a tongue-in-cheek shorthand for extreme horror or evil.
Cthulhu resides in the Tower of Will that exists in the Kadath Mandala. Zula tells the story of Cthulhu as the master of oceans and the Mu continent and how even now he is sealed in the sunken city of the Pacific Ocean, R'lyeh, but will not die. From the bottom of the deep sea, he gives people bad dreams, devouring his followers' souls, waiting for the day he will once again take control of the world above the ground and how that day will inevitably come. When the stars show the right way once more, the old rulers will resurrect countless relatives, regaining control over the universe.
The group's anger at Zula's words allow them to reject Cthulhu and what he stands for, allowing them to defeat him in battle and gain the Trapezohedron of Will.
This version of Cthulhu is a giant demonic octopus; literary accounts of Cthulhu's appearance suggest it is humanoid.
For unknown reasons, the design for Cthulhu in Shin Megami Tensei II incorporates a human penis as a tongue. This penis tongue does not appear on his sprites in II, if..., or Persona 2: Eternal Punishment.