The narrative begins in the final days of the Pre-Cataclysmic Age, marked by the civilizations of Kamelia, Valusia, Verulia, Grondar, Thule, and Commoria on the Thurian Continent. In this ancient age, the Picts, Atlanteans, and Lemurians, tribes residing on isolated islands, remain apart from the thriving civilizations. A devastating Cataclysm disrupts this age, sinking Atlantis and Lemuria and reshaping the continents. The Atlanteans, Picts, and Lemurians face adversity but survive, although they regress to primitive ways.

In this post-Cataclysmic world, the Picts and Atlanteans wage fierce wars, halting each other’s cultural development. The Lemurians, enslaved by an eastern race, revolt after thousands of years, leading to the establishment of Stygia in the south. Meanwhile, the Zhemri in the southeast begin reviving a shadow of civilization. In the north, a hardy people known as the Hyborians emerge and begin migrating southward, marking the dawn of a Hyborian expansion.

The Hyborians establish the first stone fortress of Hyperborea, which catalyzes their transformation from hunters into city-dwellers. As Hyborian tribes spread and conquer, they found kingdoms, including Aquilonia, Nemedia, Brythunia, and Koth. Their power extends widely, though they remain in constant tension with the Cimmerians in the north, who descend from the ancient Atlanteans. To the east, Lemurian descendants known as Hyrkanians establish Turan, while other Hyrkanian clans encroach on Hyperborean borders.

The height of Hyborian civilization sees the kingdoms expand and mix racially with conquered tribes, creating a complex cultural mosaic. Eventually, however, the Hyrkanians, Picts, Cimmerians, and Æsir from the north begin to challenge the Hyborian dominance. Aquilonia's overreach leads to alliances forming against it, and repeated invasions by Hyrkanian forces weaken the western empire. Additionally, a Nemedian priest named Arus, attempting to convert the Picts, inadvertently empowers them with knowledge of ironworking. Under Gorm, a formidable Pictish chief, the Picts become a rising force, ultimately invading Aquilonia and contributing to its downfall.

As Hyborian kingdoms fall, the remaining Picts and Hyrkanians carve out new empires, while the Æsir and Vanir from the north descend to further destabilize the region. The surviving Hyborians and allied Æsir establish strongholds, but the arrival of a glacial age pushes them to migrate or perish. The Æsir conquer Hyperborea, and Cimmerians sweep across former Hyborian lands, eliminating much of the Pictish influence. Eventually, the Hyborian Age world morphs into territories recognizable in modern history, and many tribes fade into myth.