"From the curious angles and proportions of the passage, Conan guessed that the old myths were true; that it had indeed been the mysterious serpent-folk of prehuman times who had first raised the city of Old Zembabwei -- or at least laid the foundations on which the present city was built. He had seen that strangely angled masonry twice before in his long career: once in a ruined castle on the grassy plains of Kush; and again, years later, on the Nameless Isle in the uncharted Western Ocean." -- L. Sprague de Camp and Lin Carter: "Red Moon of Zembabwei"
Also called Zimbabwe, a powerful black kingdom lying south and east of Punt. It was ruled by Twin Kings and had everglade flatlands in the north, merging into thick tropical jungle toward the south and east. The upper Styx formed its western boundary; a large river in the northeast and barren plains in the south are presumed to delineate other frontiers; while in the east its lands stretched to the Southern Ocean shore.
The warriors of Zembabwei were an offshoot of the Kchaka, a powerful tribe of the interior of the Black Kingdoms. When the Zembabwans were driven from their homes by a more powerful tribe, they fled east, eventually reaching the ruined city which is now known as Old Zembabwei. The nearby tribes held the region to be cursed, leaving the city free for the Zembabwans to inhabit, and build a new city upon the ruins.
For millennia, they fought the giant wyverns which soared over the jungle from cave-lairs in an eastern mountain range. A hero of the tribe, Lumbeba, traveled to the mountains and stole some eggs. He reared the hatchlings, and discovered that they could be tamed and used for riding. This enabled the Zembabwans to extend their rule over the neighboring tribes and form the present kingdom of Zembabwei. Lumbeba was immediately elevated to the throne.
Lumbeba was one of a pair of twins, and devoted to his brother. When he announced a revelation from the gods, that henceforth the Zembabwans would be ruled by twins, no one protested. Since that day, Zembabwei was ruled by twin kings selected from all the twin boys in the kingdom. To avoid conflicts over the succession, it became the custom that when one of the pair died, the other either killed himself or was driven from the kingdom. Afterward, the priests selected a new pair of twins from the young men of the kingdom and declared them the new kings.
Zembabwei's Northern Capital was its major trading center. To the south stood Forbidden City or Old Zembabwei, a religious and administrative center closed to foreigners.
Zembabweans were great traders and potential empire builders among their weaker neighbors to the west, who were justifiably suspicious of the glittering entrepreneurs who built fortresses at the same time as trading posts.
The Zembabwans worshipped Set the Serpent-God under the name of Damballah, until Conan interfered in their affairs.
References: Jewels of Gwahlur, Black Sphinx of Nebthu, Red Moon of Zembabwei, Shadows in the Skull.