"'The southwestern shore is held by the Hyrkanians for hundreds of miles. We still have a long way to go before we pass beyond their northern boundaries. I intend to go northwards until I think we have passed them. Then we'll turn westward, and try to land on the shore bordered by the uninhabited steppes.'
The fabled "Wolf-land" of demons and sorcerers, Hyrkania has vast subhumid to semiarid tract of prairie, steppe, high desert, taiga forest, and tundra lying east of the Vilayet Sea, west of Khitai, and north of Vendhya and Meru.
The northern coast of the Vilayet is described as marshy, with snow-gleaming mountains far to the north. South of the mountains are hills, home to the dreaded savarysk, the cannibal-horse of the northern steppe.
In Conan's time it had many city-states, more or less firmly under the control of the Turanian Empire. Autonomous regions were situated along the northeastern shore of the Sea and deep into the interior, with Turanian vassals along the southeastern coast and the eastern caravan routes.
The Hyrkanians were ancestors of Lemurian people who moved into the arid eastern center of the world-continent long after their chain of islands sank during the Cataclysm. They freed themselves from servitude in ancient Khitai and began to dominate the steppes and deserts west of the Great Wall. Eventually, some of these northern Lemurians invaded the western reaches of the continent and became the ancestors of the Acheronians.
Others stayed in the Hyrkanian steppe, apparently living in enclaves among the many aboriginal tribes, until after the establishment of the Hyborian Kingdoms. Then a southern Hyrkanian clan migrated around the southern end of the Vilayet Sea and established the kingdom of Turan.
Other Hyrkanians made periodic forays around the northern end of the Vilayet to harry the outposts of Hyperborea; but their raids did not amount to much until after the era of Conan. In Conan's time, citizens of the Turanian Empire were proud of their Hyrkanian heritage and likely to refer to themselves as Hyrkanians.
Wizardry was admired and respected by its inhabitants. They were horse warriors and shrewd traders, defending their caravan cities against all comers and completely dominating the Vilayet Sea. They maintained close ties with the Hyrkanian tribes east of the Vilayet, who were at least nominally part of the Empire of Turan.
References: Hyborian Age I, Tower of the Elephant, Hawks Over Shem, Black Colossus, Curse of the Monolith, City of Skulls, Road of Eagles, Return of Conan, Conan the Marauder, Conan of the Red Brotherhood, Conan - Scourge of the Bloody Coast, et al.