I wish I'd read this one first before some of the other Atheus-related subs. This gives me a better sense of things.
Giving this a 3.5/5, but only because it's light on details. Hopefully many of those details will be filled out in other subs. (I always struggle with figuring out how much to put in one sub and when to split it out into others, knowing I risk a lower score on the individual ones when I do.)
Looking forward to reading more, including catching up on the history.
My first thought while reading this: Damn, I wish I had the video game. My second: If I keep reading I will already know what happens and I can never be the player who gets to explore this place. My third: Screw it, I need to know what's happening.
I was not disappointed.
I wish I had more to add to the discussion but the other comments have all said what I wanted to and more. I too would love to see a bestiary; when is this happening? ;)
Your descriptions are great and the concepts excellent. Your mind must be a twisted place!