As I usually preface before I rip into something like this... Don't think I'm doing it because I don't like the story. If I didn't like the story, I WOULDN'T BOTHER. I think my record will CLEARLY show that I enjoy the story a whole hell of a lot. So, when I see a chapter that I think wasn't quite up to your usual standard, I gotta point out the problems I see.
Anyways, as always, all opinions are mine, feel free to use what you like, ignore what you don't, and to quote an absent friend:
Brian Randall said:
I handle other fanfic authors Nanoha-style. Grit those teeth! C&C incoming!
Prepare to be befriended!
My main problem is that this chapter felt very tell, not show. Very, very exposition-y.
The info dumps came across almost as villain monologues from Mayhem, which is entirely out of character for her. I honestly can't envision a situation where she'd spell out all the reasons and future plans like that. She already KNOWS all of it, so this comes off very "As you know, Tom...."
That same thing applied to Saint's torture. It was very... mechanical. Very much felt like a "this is a horrible thing, thusly I should make it happen" situation. (I'm going to bet it was a case of wanting to get something written and out?) A large portion of it is that it's MAYHEM. When you have a power that'll directly create pain, there's no NEED to go carving someone up. It's inefficient and SLOW. It requires no creativity at all. (And when you think thirty times faster than a human, you can come up with some REALLY inventive options instead of just "cut things off." Hell, CRICKET showed more psychological creativity than Mayhem, here.)
Honestly, in Mayhem's place here, I would have hit Saint with the direct pain a few times first. Just to show that she can. ...and THEN pull out the knives. Knowing that someone is about to carve you to pieces because they WANT to would strike me as much, much worse than someone cutting you up just to get information. (Look at Jack Slash. There's a LOT of monsters in Worm. But Jack is GLEEFULLY monstrous. Everyone knows that he does what he does because he LOVES DOING IT. And that's incredibly fucking terrifying.)
In addition, letting Saint respond here and/or defiantly spit takes away from Mayhem's momentum. I think letting him get out "I-" and then cutting off with "-was lying about having powers. etc." works better. It takes away Saint's agency, which is an enormous part of the point here, especially if Mayhem really DOES want to see if Saint will trigger. Just pain isn't enough. The psychological part is just as important.
(Instead of having the internal monologue on how Mayhem took down the Dragonslayers, I would have had him detailing to Saint EXACTLY how easy it was to destroy them. Really rub in how badly they failed and how incredibly BAD they actually were at their self-appointed jobs. Kick down a few more of his mental stabilizing blocks. Have him do it while Saint was screaming futilely after the first thumb goes away or something.)
As for the testing scene... I actually liked that bit. It's really NICE to see someone who wants to know EXACTLY what they can do with their powers. But, again, the internal monologue makes no sense for Mayhem. She already knows all her plans. But, if CRICKET needed to know why, exactly, her not-a-girlfriend-shut-up-I'm-not-gay! was turning her leg into paste.... We still get the data dump, but it can be slimmed down into something easily digested by a non-Tinker mind.
("I'm testing my toughness, so I know how much I can reinforce myself later." "...aren't you already reinforced?" "Not like this. I'll be making redundant systems, etc etc etc")
Anyways. I think I babbled and meandered a bit there, but... I hope my main concerns got through clearly. Keep up the good work, sir!