Natives of the cold black depths of the Atlantic, the Deep Ones are rarely seen by the light of day, even more rarely at the water's edge. The sea has kept its carnivorous secret, other than what is recalled in fisherman's tales or turn-of-the-century fictions.
These clammy, ancient creatures are humanoid but share little with humanity, more akin to the deep-sea terrors that are only occasionally witnessed or washed ashore. If they once had society or civilization, no evidence remains, at least none explorable by man under the great pressures of the abyssal trenches. Indeed, the Deep Ones' preferred method of feeding is to drag victims into a death-dive until the unfortunates are crushed into more edible material.
Just as animals react en masse to upheavals in their environment, so too have the Deep Ones responded to the doom that has come to New England. For the first time in lifetimes they have emerged from the waves, slick and dripping, losing little of their sea-quickness even on two legs. The warbands of the Draug drive them ahead like cattle, or leave them to lurk in slime-bound rock pools and inlets. They dispassionately observe the changing coast from behind shark-dead, unblinking eyes.
The source of this information (the secret world website)