I'm a person who rarely gives a grade below 6, but in this case I had to.
From what I understood there's a gate, called the Divine Gate that if you reach it you can modify the whole world the way you want it
The story is fair, if it was told the right way, it could be good, but they made it so bad.
This anime is an action, fantasy and sci-fi, so it is mainly an action anime, which is not good, the fighting scenes are short and most part of them are pretty bad. Basically the most important part for this anime to be good was bad, the only way to save this anime was the course of the story, that didn't saved it al all, also this is not a complete anime, it doesn't ends the story, it ends urging a new season.
The art has some 3D aspects, they are not bad, but neither are OK, I would say they are mediocre, 3D animation actually is something that usually doesn't please people, so that makes it worse for the anime image, even the 2D animation is not good.
The sound, if I have to say I think it is the only thing that is actually "good" of this anime, the OP is pretty good, the ED is good, the OST are fine.
The characters are pretty bad though, they have bad motivations, they have strange pasts, and made strange choices all their life, the protagonist is very dumb though, he is always blaming himself for things he didn't do, there are characters that according to MAL are main characters, but they hardly appear, I really can't understand it, the others main characters are not bad, but also not good.
I did not enjoyed this anime, don't really know why I watched it until the final, I think in the two or three last episodes I was curious about what would happen, maybe that's a good point about this anime, I recommend you not to watch it unless you really have nothing to do.