Ok well its a little early for one of these because I only have the prologue out but if I don't do it now I'll forget
Prologue is really quite short. There's only a few problems, besides that. The comma usage is the biggest problem I see. "They were created by a thing called, Hell's Gate." It would sound better like, "They were created by Hell's Gate." Or "Hell's Gate was the thing that crested these things." Another one: "Although that is great there are things much, much worse that have taken their place." That just needs an extra comma and a little tweaking. "Although that is great, there are things that are much, much worse which (I'm not sure about the which) have taken their place." So just watch those commas and lengthen everything a bit.