Les Amis Improbable
The sprawling empire of Thassilon covered much of the known world thousands of years ago and was powered by conquest and sophisticated magic. Thassilon was ruled by god-like wizards wielding a type of rune magic whose secrets even the most learned scholars today can only guess at. With the labor of their enslaved giant armies, these wizard-demigods built immense magical monuments, many of which lie in visible ruins today (many of the ruins in Varisia are exceptionally well-preserved). The purpose of most of these structures has been lost to time, but sometimes traces of their ancient magic remains, much to the chagrin of those who would explore these ruins further.
Thassilon was completely destroyed, and its surviving pockets of population forced into a tribal existence by an unknown cataclysm.