The Lost Empire of Serredin

The Lost Empire.
The Primitive human settlers that have roamed Abexilas for millennia, the Elumites, are stagnant and feral. Yet scattered throughout the continents are far more ancient structures, There has been no crossover event from Ratham to Abexilas ever in recorded history. Manned flight to and from each planet was impossible even before the Comets arrival. Upon close investigation I see fit that some long lost and unknown people besides the Elumites must have been the builders of the known world. The Iku'su'ru tribes in the Great Mesas of the west have roamed the lands for centuries, however they are far too primitive to have been the creators of such intricate creations. The Villager race while being Planet spanning because of some unknown event, are also unable or unwilling to build anything of substantial size, also they still exist around Abexilas in a sizeable force so why would they let such magnificent cities fall into Ruin? My Friends I have found one possible race, one possible group of people long forgotten to the winds of time. My friends I propose that Jagdisans in some point in time arrived on Abexilas. The records of the Jagdisan destruction are incomplete at best and its not far out of the way of understanding. My best and only link to this possible history is the historical records of the Long Dead Empire of Serredin.