Homebrew Deep One Species Details

I shall plan my cousin’s escape from that Canton mad-house, and together we shall go to marvel-shadowed Innsmouth. We shall swim out to that brooding reef in the sea and dive down through black abysses to Cyclopean and many-columned Y’ha-nthlei, and in that lair of the Deep Ones we shall dwell amidst wonder and glory for ever. - H.P. Lovecraft, The Shadow Over Innsmouth

Locked in the timeless depths of the sea, their alien and arrogant lives are coldly beautiful, unbelievably cruel, and effectively immortal. They are a marine race, unknown in freshwater environments, and globally have many cities, all submerged beneath the waves.

Creatures of the Living Sea

Deep Ones are immortal until slain (so are any hybrid offspring), and may be worshipped by humans. From time to time, the Deep Ones establish and foster relationships with isolated human communities, offering to trade golden treasures from the depths of the sea, along with bountiful fish catches, in return for certain promises. Such communities eventually fall under the grip of the Deep Ones, and any dissent either evaporates or is fiercely dealt with. Such humans willingly accept the Deep Ones, Dagon, Hydra, and Cthulhu as their master, as the gift they bestow are wondrous (at least, at first), and their god's will is demonstrable in both tangible and beneficial terms

Aquatic Deal Makers

The religion offered by the Deep Ones usually takes the form of certain oaths, offered at rising degrees of "membership", that commit human worshippers to certain agreements. While appearing beneficial and relatively innocent at first, it is not long before the Deep Ones begin to demand more, even to the point of requesting human sacrifices. Such people devote themselves to the Deep Ones, with some eventually taking the Third One, entering into breeding rites to produce hybrid offsprings to further promote the Deep One race.

With such historic links with humanity, the Deep Ones have an extensive network of human (hybrid or otherwise) supporters, who act to further the will of the Deep Ones, which usually takes the form of "disappearing" those who would broadcast knowledge of the reality of the Deep Ones, ensuring human-hybrids can "find" their way to the Deep Ones when the "change" comes upon them, and planting seeds to foster new worship in out of the way communities.

Variable Features

The Deep Ones are humanoid beings with fish, human and amphibian-like traits, they are described as having grey-ish green, glossy and slippery skin with white stomachs. They have scaled, ridged backs, as well as webbed and clawed hands and gilled necks. Notably, they have heads similar to that of a fish, with mouths filled with sharp teeth and eyes incapable of blinking. They move about in an inhuman fashion, by hopping oddly, and occasionally move on all fours. Deep Ones can be anywhere between 3 and 7 feet, and weigh anywhere from 50 to 300 pounds.

 

Deep One Traits

The Deep Ones have a number of skills and traits, detailed here.

Amphibious

Your gills allow you to breathe air and water and are not subject to negative effects from water pressure. Additionally, you have resistance to cold damage.

Darkvision

Life underwater has accustomed you to darkness. You can see in dim light 60 feet ahead of you as if it were bright light, and in darkness as if it were dim light. You can discern color in darkness.

Predator's Fangs

Life underwater has accustomed you to hunting smaller fish. Your fangs can be used as an unarmed strike that deals 1d6 + your Strength modifier piercing damage. 

Great Old One Ties

You have blood tracing back to the Great Old Ones themselves. You can communicate with fish and cast Commune once per day to contact Dagon, Hydra, or another fathomless entity of a higher being. Whether or not this allows the Deep One to contact those as high in status as Cthulhu or the Kraken is at the discretion of the DM.

Ability Score Maximum

You get a +2 to Strength and +1 to Constitution.