The Thurian Age was a specific epoch of Earth's pre-history. Kull (created by Robert E. Howard) lived in this period. It predates the Hyborian Age of the Conan the Barbarian stories and is known to them as the Pre-Cataclysmic Age.
The main continent is called Thuria, although smaller continents such as Atlantis and an unnamed Eastern continent exist, as do several island chains. Most of the planet is unexplored wilderness inhabited by "scattered clans and tribes of primitive savages."
A great cataclysm ends the Thurian Age some time after the Kull stories. Several countries sink into the sea, others rise from it, and the rest is devastated by earthquakes and volcanoes. Civilization is destroyed and the survivors attempt to build a new culture but warfare and a Lesser Cataclysm strike, creating the Hyborian Vilayet Sea and destroying any last remnants of Thurian society.
Six kingdoms dominate the main continent of Thuria. All share a common language and possibly a common origin. East of these kingdoms is a vast desert. The six kingdoms are all part of the "Seven Empires" although the seventh member is never named.
There are three main barbarian societies in the Thurian Age:
Another mysterious kingdom lies on the east coast of the Thurian continent. They have some contact with Lemuria but come from another continent entirely to the east of the Lemurian islands.
The Kull story The Shadow Kingdom refers in passing to two other countries, Mu and Kaa-u. Mu sinks during Cataclysm and its mountains become the islands of the South Seas.
An untitled draft in the "Kull of Atlantis" stories mentions 3 other nations: Farsun (enemy of Thurania, described as west of Valusia), Zarfaana (east of Valusia, the Camoonian Desert separates the two and there is a sea to the north of Zarfaana), and Thurania (south of Zarfaana, enemy of Farsun).
There are other "equally civilized" but non-human kingdoms. The citizens were of one or more older, pre-human races. One such mysterious pre-human civilization exists at the south of Thuria, this country is, at first, untouched by the Cataclysm. When the oppressors of the Lemurians are overthrown, however, the survivors escape to this region and destroy it in turn, creating the new country of Stygia.
- Robert E. Howard - The Hyborian Age (1936)
- Robert E. Howard - The Shadow Kingdom (1929)
- Robert E. Howard - Kings of the Night
- Robert E. Howard - The Isle of the Eons (unfinished fragment)