This would be the final book in the series. Half the world is gone. Whatever remains has fallen into chaos, and all live in a post-apocalyptic world where man and beast are at war. 

I'm not too sure about the ending for this, but it won't be happy- it will most likely be a bittersweet ending. A happy ending is just too unrealistic, and I'm a little reluctant to do a full-on sad ending, so most likely I will just make it bittersweet.

I have a couple of ideas I'm playing around with, like one ending involves the pollution around remaining cities wafting away, and the sun begins to shine, which ends up stopping a battle happening below as the two sides watch in awe. But that's a bit too cheesy if you ask me.

I don't know. Another idea is that events lead to an uneasy peace between the two sides, and the animals allow the humans to rebuild- though only under their watchful eye, as they make sure no such atrocity is committed against them ever again.

This book will definitely have many new characters (I had an idea for a friend group between a machine, a human, and an animal {likely a neoraptor}). And there will be a lot of major death, more so than the previous two novels (though it won't have every single character dying in the end like the original did).

I don't know, this is the most vague one of the RoW books, but I haven't even finished the final draft for the first one so I have a lot of time.