Kuo-toa

In the Dungeons & Dragons roleplaying game, the kuo-toa are fish-like monstrous humanoids that dwell in the Underdark.

Creative origins
The name "Kuo-toa" was created by Gary Gygax, co-creator of the Dungeons & Dragons roleplaying game, and first appeared in dungeon module D2 - Shrine of the Kuo-Toa. However, the concept was clearly inspired by the Deep Ones, creatures that appear in H. P. Lovecraft's novella "The Shadow Over Innsmouth". Like the Kuo-toa, the Deep Ones are a monstrous marine-dwelling race of fish-headed humanoids, who worship a being called Dagon. The kuo-toa is considered a "Product Identity" by Wizards of the Coast and as such are not released under its Open Gaming License.

Description
Kuo-toa have scaly, bipedal bodies with fish-like heads.

Society
Kuo-toa often raid seaside settlements for human victims. Most worship the goddess Blibdoolpoolp, though a few remote tribes worship Dagon.

Kuo-toa in the Forgotten Realms
In the Forgotten Realms campaign setting kuo-toans maintain friendly relations with drow, their Underdark neighbours. Blibdoolpoolp is the focus of the kuo-toans' lives, and even has her own monstrous, deformed kuo-toa breed - the giant kuo-toa leviathan. They have total hatred for the sahuagin, another race of fish-like beings.

Kuo-toa in Greyhawk
In the World of Greyhawk campaign setting, kuo-toa settlements are known to exist in the Underdark, near the Vault of the Drow beneath the Hellfurnaces.