Conan the Barbarian and the map of Hyboria-Stygia

STYGIA

"Ships did not put unasked into this port, where dusky sorcerers wove awful spells in the murk of sacrificial smoke mounting eternally from blood-stained altars where naked women screamed, and where Set, the Old Serpent, archdemon of the Hyborians but god of the Stygians, was said to writhe his shining coils among his worshippers."

The Hour of the Dragon

After the great catyclsm caused the sinking of Atlantis and Lemuria, many Lemurians made their way to the Eastern coast of the Thurian continent, only to be enslaved by the ancient race which already dwelt there. Rising to destroy their powerful masters, they were left stalking the ruins of a strange and ancient civilization. The remaining survivors of that civilization moved westward, overthrowing the pre-human race of serpent-folk of the south and founding a new kingdom called Stygia. The Stygians were an ancient race, a dark, inscrutable people, powerful and merciless. Their rule had once stretched far north of the river Styx, beyond the meadowlands of Shem, and into the fertile uplands now inhabited by the peoples of Koth and Ophir and Argos. Stygia was bordered by the kingdoms of Kush, Darfar, and Keshan. It's western boundary was the Western Ocean, and also the river Styx, the real border of Stygia. This river, springing from a nameless source far in the unknown lands south of Stygia, ran northward for a thousand miles before it turned and flowed westward for some hundreds of miles, to empty into the Western Ocean. The river Styx supported workable, cultivated lands. The further away from the river, the less workable the land. The Stygian borders of long ago had once met the boundaries of ancient Acheron.

The Stygians did not base their glory and power on ships and fleets, as they had trading vessels and war galleys. However, these fleets were not in comparison to their inland strength. Many of their crafts moved merchandise and slaves up and down the river Styx, rather than along the coasts of the Western Ocean. Bringing in raw materials and slaves out the Black Kingdoms, Sukhmet and Kheshatta were presumably caravan cities that serviced such traders. Caravan routes were common and numerous, and ran in many different directions through the country. Strangers were not welcome in the cities of Stygia as they were allowed inside the country only when they came as ambassadors or licensed traders.

Near the river's mouth dwelled the great black walls and towers of Khemi. Khemi was Stygia's greatest port, and perhaps it's most important city. Khemi was not like the seaports of the Hyborians, where types of every race gathered, traded and sold. The only foreigners found here at the ports were negro and Shemite slaves. However, no one was allowed ashore after dark. The king's seat was that of ancient Luxur, but in Khemi the Priests of Set were the real power, and it was said that the center of Set's religion and Stygia's power lay further inland, in a deserted city near the bank of the Styx.

The terrain of Stygia is described as having forests, marshes, and numerous islands along the Western Ocean. Further inland the land is mostly bare desert, it's scene only broken up with tombs and ancient ruins. The ghost-haunted Swamps of the Purple Lotus were located in the southern grasslands, the jungle beginning near the borders of Darfar and Keshan.

The ruling class of Stygians were dusky, hawk-nosed, and haughty. The warrior castes of the Stygians were a tall, muscular race with skin bronzed by the sun, and dark hair, while the lower classes were a mixture of Negroid, Stygian, Shemite, and Hyborian.

Here is another map of Stygia from Conan the Rebel written Poul Anderson, published by Bantam.