This was requested by @TheGwen2903I hope it helps. XOXO BUTTERBALL.

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Cthulhu

Origin:  Cthulhu Mythos (Unlike most mythical creatures, Cthulhu's mythology comes from fiction novels which over time along with a cult following has caused it to become a mythological creature on its own.) First appearance, Call of Cthulhu in 1928.

Summary and or Explanation: Cthulhu is a cosmic entity created by writer H. P. Lovecraft and first introduced in the short story "The Call of Cthulhu", published in the pulp magazine Weird Tales in 1928. Considered a Great Old One within the pantheon of Lovecraftian cosmic entities, the creature has since been featured in numerous popular culture references. Lovecraft depicts Cthulhu as a gigantic entity worshiped by cultists. Cthulhu's anatomy is described as part octopus, part man, and part dragon. Its name was given to the Lovecraft-created universe where it and its fellow entities existed, the Cthulhu Mythos.

Though invented by Lovecraft in 1926 the name Cthulhu is probably derived from the Classic Greek word chthonic meaning "subterranean", as apparently suggested by Lovecraft himself at the end of his 1923 tale The Rats in the Walls.

Cthulhu has also been spelled as Tulu, Clulu, Clooloo,, Cthullu, C'thulhu, Cighulu, Cathulu, C'thlu, Kathulu, Kutulu, Kthulhu, Kthulu, Q'thulu, K'tulu, Kthulhut, Kutu, Kulhu, Kutunluu, Ktulu, Cuitiliú, Cqulu, Thu Thu and in many other ways. It is often preceded by the epithet Great, Dead, or Dread.

Lovecraft transcribed the pronunciation of Cthulhu as Khlûl′-hloo and said that "the first syllable pronounced gutturally and very thickly. The u is about like that in full; and the first syllable is not unlike klul in sound, hence the h represents the guttural thickness." An approximate IPA transcription, based on this description and the non-IPA signs, would be [(k)ʟ̝̊ʊlʔɬuː], with a voiceless velar lateral fricative. S. T. Joshi points out, however, that Lovecraft gave several differing pronunciations on different occasions. According to Lovecraft, this is merely the closest that the human vocal apparatus can come to reproducing the syllables of an alien language.

Long after Lovecraft's death, the spelling pronunciation /kᵊˈθuːluː/ kə-thoo-loo became common. The role-playing game Call of Cthulhu has used the pronunciations 'klhul-hoo' or 'tluhluh'".; or more recently 'kuh-THOO-loo'";

In "The Call of Cthulhu", H. P. Lovecraft describes a statue of Cthulhu as "A monster of vaguely anthropoid outline, but with an octopus-like head whose face was a mass of feelers, a scaly, rubbery-looking body, prodigious claws on hind and fore feet, and long, narrow wings behind." Cthulhu has been described as a mix between a giant octopus, a man, and a dragon, hundreds of meters tall, with webbed human-looking arms and legs and a pair of rudimentary wings on its back. Cthulhu's head is depicted as similar to the entirety of a gigantic octopus, with an unknown number of tentacles surrounding its supposed mouth.

Simply looking upon the creature drives the viewer insane, a trait shared by many of the Great Old Ones and Outer Gods.

(So this reminds me of the game Call of Cthulhu dark corners of the earth where the town is inhabited by fish people. Some of the more technical stuff is from Wikipedia I may know a lot but I don't know everything about Mythological creatures.)