Okay so mr parasyte is kinda based rn
my main of three guesses is that the beast are meant to protect the remaining humans and keep their numbers down to like prevent awakening/angering/ect some greater power (gurren laggann style)
There is a reason the past humans were apathetic to their demise, especually considering they had a hero (to protect somthing) and such powerful magics, if there was I doubt they would of so casually been so apathetic if it werent a part of a greater cycle
