Sorcery in Shad — Brian Lumley

Pity the poor lamia! Mighty Orbiquita, she who damned to death countless men for merely looking at her, she who slew with impunity any who dared breach the walls of her fabled castle . . . Orbiquita has fallen in love--and with a barbarian Hrossak!
Tarra Khash, he is, who saved a lamia's life and made her long to be human again. Tarra Khash, who with the help of the last survivors of an alien race, overthrew a god and saved an entire city thereby. Tarra Khash, who has adventured far and wide through the Primal Land, searching for treasure, for wine, women, and song.
Tarra Khash, who has fallen into the clutches of the slave Cush Gemal, who was once an ordinary man but who has become the foulest of sorcerers, Black Yoppaloth. Like all sorcerers, Black Yoppaloth craves immortality, and believes he stands on the brink of achieving it. Then his evil power will be unrivaled and he will control all of the Primal Land.
Only Tarra Khash stands in his way. Tarra Khash--and, though he does not know it, his friends and allies: she who was once the lamia Orbiquita; the alien Amyr Arn; a slumbering, ponderous yet powerful moon god; and the magician Teh Atht, who must choose between immortality and saving the Primal Land!