Deep Ones are a species of aquatic monstrosities which feature prominently in H.P. Lovecraft’s Cthulhu Mythos.


Humanoid in appearance, Deep Ones are primarily aquatic in nature although they are capable of surviving on land for an indefinite period of time. They are hairless, have a scaly fish-like skin, feathered gills on their necks or upper torsos, and are possessed of webbed hands and feet which facilitate travel beneath the waves. Their heads are said to resemble those of frogs or fish, and they sport large, unblinking eyes which give them excellent sight in the depths of the ocean. Deep Ones are functionally immortal, and will never die unless subject to violence or accident. In addition, for reasons unknown, some Deep Ones will continue to grow over the course of their lives and become creatures of truly gargantuan proportions.


Deep One Hybrids

The hybrids are a result of the pact made between the Deep Ones of Y’ha-nthlei and a man named Obadiah Marsh at some point during the nineteenth century (see below). A hybrid is created through the cross-breeding of human females and Deep One males. These offspring are born as seemingly normal-looking human babies, but over the course of their lives slowly transform into fully-fledged Deep Ones. At this point they leave their landward homes and settle in one of the great oceanic metropolises maintained by their kin beneath the waves.


Whilst some unverified legends tell that the Deep Ones came to Earth from a distant star system many years ago, what is known is that they have existed as a species with a high level of technology on this planet since long before mankind learned to walk upright and use tools.


Little is known of the actual social practices of the Deep Ones, although their cities have been noted to possess a certain grandeur which some have compared to the edifices built by the Roman Empire in times past. These structures are said to bear many similarities to the colonnaded temples and great frescoed halls built by the Romans, although as may be expected, the carvings of the Deep Ones depict scenes from their own history, and as such can be almost indecipherable to a human viewer.

Deep One Cities

Deep Ones, being creatures of the seas, prefer to build their cities on the ocean bed, far from the prying eyes of land-dwelling species. Currently there are four known Deep One cities, although there are undoubtedly more secreted away in the deepest oceanic trenches or beneath the polar ice floes.


  • Located just off Devil’s Reef near Innsmouth harbour, the inhabitants of Y’ha-nthlei shared a mutually beneficial relationship with the mortal population of Innsmouth until recently: in exchange for breeding stock of humans, the Deep Ones provided the township with fertile fishing grounds and a supply of exotic golden jewellery which was used to fund the town in times of hardship. Unfortunately, the existence of Y’ha-nthlei was uncovered by the United States government during a covert operation in 1928. The authorities used powerful explosives and submarine-launched torpedoes to attack the city, but recent events suggest that it may have survived this onslaught (See main article: Innsmouth).


  • An undersea metropolis located just off the coast of Cornwall, very little is known of Y’hloa.


  • Another mighty Deep One habitation, this one situated near Iceland in the vicinity of the volcanic island of Surtsey.

Ya’ Dich-Gho

  • The City of Ya’ Dich-Gho was formerly situated off the coast off Sweden, but was accidentally destroyed during military manoeuvres in 1982 whilst surface ships hunted for simulated submarine contacts.


The Deep Ones are known to venerate their own perverse “holy trinity” of gods, comprising the Great Old Ones Father Dagon, Mother Hydra and Great Cthulhu himself. Indeed, Cthulhu has even gone so far as to entrust the guardianship of his “daughter,” the fell beast known as Cthylla, to the Deep Ones, who have secreted her away in one of their oceanic fortresses somewhere beneath the North Atlantic.

The Deep Ones of Y’ha-nthlei are also known to venerate a trio of colossal monsters known as the Silent Ones, although their exact relationship with these creatures remains unknown.

Other Deep Ones have also been known to employ the services of the amoeboid monstrosities called Shoggoths, although what the terms and conditions of these contracts are is anybody’s guess. Yet more offer their services to other fell beings, although the reasons behind these allegiances remain largely unrevealed.

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