The creatures of the eastlands abhor the west, the reason for this more because of the opinions passed down from generation to generation. Their teachings are that they are the rightful rulers of JERA, and that the humans and elves are former slaves who they have every right to capture, that they are their property. This is the official dogma, but many of the creatures of the east do not believe this way and in secret wish that they could escape to these lands of freedom and live amongst them, except that the mannish races will not allow it, or at least so they are told.
The lands themselves are polluted, horrible places to live near the cities or the ruins of the former cities. Slowly nature begins to mend the damage done to the creatures of the world. The mutated forms of former humans and elves are beginning to mend their genetic code to match closer and closer to the original. This process has taken a few hundred years so far, but the Overseer has kept careful track of the changes and quantified them. He came to the conclusion that in another couple hundred years, the "monsters" of JERA will almost be back to their original selves. If this happens, he sees that the hatred of the east will wane and no revenge will ever be likely, especially considering the openness with which cities like Trondheim and Grunburg have welcomed the monsters into their society (though in Grunburg, they are still treated as second rate citizens).
He hates the humans for attacking with the weapons of mass destruction that polluted the land and hates the elves both for "abandoning" the remainder of the elves when they took to the skies as well as possessing extreme jealousy for their undefiled appearance and the rebirth of their culture, something that died out centuries ago for his people. The elves, upon their return, saw the creatures of the continent of Asterland as hideous reminders of their former mistakes, something that they had taken great pains to write out of their own history books, or at least the ones accessible to the common man. Thus they made no effort to get along with the creatures of the world. In fact, they took advantage of them upon their return, which saw them almost as gods, much in the same way that the native Americans treated the white men when they came to the new world. This abuse of trust caused much of the wish for vengeance that the monsters feel for the elves.