The Sleeping Age was a time in which all the remaining humans on Gohr existed inside Bunkers deep underground.
They remained there for several hundred years, the bunkers using nuclear fusion power generators, massive recycling facilities, and automated crop systems. Eventually, however, these machines broke down. Without anyone to repair them, The People were forced to return to the surface. Some bunkers, however, weren’t as protected as others, and radiation leaked in, slowly changing the Human’s DNA from it’s natural course, and turning them into different creatures. In those bunkers where the radiation was too intense, or the mutations were too severe to live with, the inhabitants died, leaving the bunkers sealed and unknown to The People who did survive.