The kuo-toa are fish-like amphibious humanoids of Dungeons & Dragons, drawn as half-mad religious zealots. They are the degenerate descendants of a once-great race pushed deep underground long ago, and they worship mad gods, spawning new numbers as they dream of the day they retake the surface. Nearly exterminated, they plot their return with glee — which is what makes them so warped.
They chiefly worship the dark goddess Blibdoolpoolp, and some venerate Dagon instead. A fallen race going insane in the dark, forgotten yet endlessly breeding and scheming to reclaim a surface world that has forgotten them, rhymes with the Deep Ones’ worship of Dagon and with our world’s motifs of proliferation and return.