Deep One

Their croaking, baying voices, clearly used for articulate speech, held all the dark shades of expression which their staring faces lacked ...

They were the blasphemous fish-frogs of the nameless design—living and horrible.A very similar description is provided in the much-earlier story Dagon: I think that these things were supposed to depict men—at least, a certain sort of men; though the creatures were shewn disporting like fishes in the waters of some marine grotto, or paying homage at some monolithic shrine which appeared to be under the waves as well.

Grotesque beyond the imagination of a Poe or a Bulwer, they were damnably human in general outline despite webbed hands and feet, shockingly wide and flabby lips, glassy, bulging eyes, and other features less pleasant to recall.

They worship twin deities, the cult of whom they have introduced among the human population of Innsmouth, who know them as "Father Dagon and Mother Hydra".

However, the elderly derelict (and Order of Dagon initiate) Zadok Allen invokes Cthulhu in a moment of strong emotion, and Robert M. Price has suggested that "Dagon" may have merely been "the closest biblical analogy to the real object of worship of the deep ones"[3] The Deep Ones are or were opposed by mysterious beings known as the Old Ones, who have left behind magical artifacts that can keep them in check.

The Esoteric Order of Dagon was seemingly destroyed when one of Obed Marsh's "lost descendants" sent the U.S. Treasury Department to seize the town.

The backstory of The Shadow over Innsmouth involves a bargain between Deep Ones and humans, in which the aquatic species provides plentiful fishing and gold in the form of strangely-formed jewelry.

As the hybrid gets older, they begin to acquire the so-called "Innsmouth Look" as they take on more and more attributes of the Deep One race: shrunken ears, bulging and unblinking eyes, a narrowed head which eventually goes bald, scabrous skin that transforms into scales, and a neck which develops folds and later gills.

Together with Cthulhu, they form the triad of gods worshipped by the Deep Ones (their names are inspired by Dragon, or Dagon, the Semitic fertility deity, and the Hydra of Greek mythology).

"[6] Other authors have invented Deep One cities in other parts of the ocean, including Ahu-Y'hloa near Cornwall and G'll-Hoo, near the volcanic island of Surtsey off the coast of Iceland.

The destruction of Ya' Dich-Gho is described in "When Death Came to Bod Reef"; the city's history in "Herr Goering's Artefact" and the life of the survivors in "Three Weeks of Bliss".