The Nithron in darkfall world

The Nithron built their own empire and lived in a peaceful life for nearly one hundred years since they had conquest of Agon. As time flied, the first empire became degenerate at the stage and was substituted by the second one. Unlike the first empire, lacking of authority, the empire could not control the nation any more thus it divided into many regions soon. Subsequently it came to a war age. In order to gain more resources and territory, the wars between these separate regions occurred time and time again. The questions still puzzled us today that why the Nithron disappeared so fast at that time. No exact answer has been put forward till now.