The Father of Tsotha Lanti

"I am a sorcerer, and older than men reckon, but I am human. As for Tsotha—men say that a dancing­-girl of Shadizar slept too near the pre-human ruins on Dagoth Hill and woke in the grip of a black demon; from that unholy union was spawned an accursed hybrid men call Tsotha-Lanti"
Robert E. Howard, "The Scarlet Citadel" 1933

Lemurian Demonology

Beyond the gate of Agut-atoth are demons beyond number, hungered to madness they tear eternally at the barrier. What the Elder Gods crafted the demons cannot rend asunder but the sorcerer may open the gate for a short time and call through certain things by means of the proper seal and incantations. It is done with utmost care for if the H'klim of the Elder Gods take notice they will slay the sorcerer and should the sorcerer err in the seal or formulae he will surely be consumed by what is called up.
(The Druuna-Cosan Scrolls as translated from the Aklo by Hasper Charris)