I also liked this piece. It needs a lot of polishing and cutting down, but when that's done, this will be awesome. As to the polishing and cutting down, I will second something that Ryos said:
About that exposition. The piece is very explainy. I felt like there were too many asides and too many explanations. This is a stylistic thing and therefore hard to quantify, but even your fights feel explainy. The whole thing is like a chain of explanations instead of a narrative. It gets tedious after a bit.
Yeah, and about those fight scenes. They're a bit tedious. I don't know for sure why I feel this way, but I'll try to explain as best I can. Part of it is the explainy narrative style. A large part is, I think, that most of his opponents are horribly outclassed, so the outcome of the fight is really quite obvious. Once it becomes clear that he's just going to tear through and obliterate everyone in his path, it becomes tedious to have to sit through a blow-by-blow of him doing it. The Judge fight was more interesting.
He is 100% correct in his assessment. If this is a prologue, then we just need a taste of things. A glimpse at the main character, a cool demo of the magic, and a vision of the world. It felt like you were trying to lay everything on the table here, to explain how everything worked, which isn't really necessary in a prologue. In fact, it takes some of the mystery out of things. Show us something really cool and let us wonder about the how and why. As long as it doesn't confuse us, it will whet our appetites for the explanation later.
Anyway, Ryos already made the points I wanted to make, but I can give you my own answers to your three questions:
1) Character more likable: First, make him enjoy killing a little bit less. I wondered how this man could ever be considered a "hero" when he smiles as he tears his victims to shreds. It's hard for a normal person to like someone like that. Along the same lines, a little remorse or hesitance would go a long way toward showing that he is doing what he is doing because he has to, not because he enjoys it. After all, these are people he has fought for and saved in his past.
2) Improvement on magic system: I think the magic system is great. Keep it the way it is but since this is a prologue, don't explain it so much, just show it in action. As to the stages, instead of calling them stage 1, 2, 3, you might name them. This would not only be cooler, but more in line with a fantasy setting.
3) Parkour more interesting: This one is easy, just show us what he does generally rather than blow by blow. For example, look at this excerpt:
Dariel, feet slipping against the wall, was still able to run along the stone. With that propulsion he swung himself away from the window, to another one to the left. He caught this sill with both hands and looked down. It worked. She may not have noticed him, considering the darkness. She might have been looking up for reasons unrelated to the falling dust and broken stone chips, but it did not matter.
All of the above could be said with a much simpler, "Dariel leaped from handhold to handhold, disappearing around the corner before the woman could look around." Yeah, seeing the cool handhold stuff in Parkour is awesome, but reading it blow by blow isn't. Just give us the idea that Dariel is ninja and our imaginations will fill in the blanks. Another example:
He stepped onto a low window sill and used it to propel his body to the roof across the street.
This is a great chance for you to use a metaphor or a simile for your reader to catch a visual image, something like "Dariel leaped onto a window sill and launched himself toward the adjoining roof, bouncing from wall to wall like a ricocheted lock."
I think the key to making your Parkour more fun to read is to first, simplify it from blow by blow, and second, use more imagery so that your reader gets cool mental images.
Anyway, I think you should run with this piece. I've had the same problem trying to catch up on The Name of God. It's a lot to read, and this is more interesting.
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