The Kappa are part of Japanese folklore. In 2005 they were first used as a fictional race by Chaosium for the Call of Cthulhu RPG.
The Kappa are a vampiric amphibious species. Whom are up to 3ft tall with sharp bird-like beak, a thick tortoise-like shell on their back, and lion-like facial features. They have a clammy slimy skin that changes its color to match the ambient surroundings and possess thick fatty deposits which lets them easily survive the extreme cold. Kappa have great strength and agility, for such a small species. A Kappa is strong enought to seize a human, drag him underwater, and hold him until he drowns. They consider humans to be a food source, siphoning out the blood of their drowned victim through its entrails.
Most of them live off Japan's coast, in their underwater kingdoms. Their dominions exist side by side with those of the Deep Ones, and they usually have good relations with each other. Kappa will sometimes capture humans for labor or their amusement. They worship Gol-goroth and Yig, and sometimes work for Cthulhu and his Star Spawn. Kappa possess a code of ethics, and if you show a caught Kappa mercy they will repay you with one service. It's a race whose members exact vengeance for the any perceived insult.