A entity for H.P. Lovecraft's short
story "The Call of Cthulhu" who also appears in several later stories, though CC is the only one that focuses on him. Cthulhu is a extraterrestrial being referred to as "Great Old Ones" and is generally associated with madness. It is said to have "yielded simultaneous pictures of an octopus, a
dragon, and a human caricature.... A pulpy, tentacled
head surmounted a grotesque scaly body with rudimentary wings." While no specifics of it's height have been given, in the Climax of Call of Cthulhu, when some sailors stumble upon the formerly-sunken city of R'lyeh, the city in which Cthulhu is said to be sealed, they accidentally release the
monster, and one said it was "A mountain that walks or stumbles", implying it's enormous height.
For some reason, Cthulhu along with the other Great Old Ones have been sealed away, and is said that Cthulhu one day
will awaken and release the Great Old Ones and they
will resume the rule of Earth, and there
will be a "Holocaust of freedom and ecstasy". the Great Old Ones telepathically talked with the earliest humans, and started the infamous
Cult of Cthulhu.
many real life cults have been started and can be found on the
internet. I'm not sure which scares me more, the Cthulhu cults, or the other religions.