GQFW rise of the rune lords
Not much is known about this ancient and dead civilization except a few pieces of information. Thassilon itself was a huge empire that was run by the Rune Lords. Thassilon was split into seven lands each ruled by a Rune Lord. The Sihedron appears in all the ruins in some form or another. What caused the fall of Thassilon is unclear. But the extent of its destruction has served to hinder the academic study of this once powerful empire.