Non stop violence in a post apocalyptic earth, this is so much more anime than Ghibli. It isn't actually a true Ghibli film but is often marketed as such. It's style is very different to that usually associated with Ghibli. If you're expecting 'My Neighbour Totoro', you'll be disappointed. I like Ghibli films but this falls into an anime spiral of - attack the armies that control the power and release the monster driving army2 into the acid sea who must retaliate by killing more people and raising a demon etc.
All very well for that genre but I don't tend to rate those films well. I'm really reviewing this film for Ghibli fans hoping for, "Howl's Moving Castle" so they can find something more appropriate