Alright, so this chapter establishes many things and hints at the others:
1. We're going to see even more fcked up shit from now on. Urana-sensei tackles many hard topics and we're in a kind of post-apo setting, so it's to be expected. I'm now just waiting for human cattle, as it IS a prevalent thing in many ofther post-apo worlds and would be just as messed up as what Amo endured.
2. It was quite a bizarre "divine intervention" by our angels. They didn't come there to kill the dude, so I'm a bit relieved about Legto. Didn't really want him to be some terrible scoundrel as well. They really just beaten him up, maybe even unintentionally, because they only attacked when he was about to. Probably really just wanted to take the boots off of him.
3. It seems like they're kind of keepers for precious items, maybe exclusively concerning the Watchman Series, maybe not only that. They make sure a right person has an item, that it's not polluted maybe or used in a way they don't want, by wrong people. What made Amo qualify as the right person? Who knows. Maybe that terrible abuse? Maybe that's what angels want - to give those items only to tortured souls?
4. If we try to connect it all, the book might've been a part of a set, not just ABOUT the set. And maybe Legto was not the right person to have it, by angels' standards? And since he didn't want to give it to them, he got killed? Might be the case.
5. Since the angel only gave Amo boots "for the time being" and she's supposed to give it back (or they will take it back, more realistically), that might be the case for everyone. Maybe those items are supposed to flourish and develop in hands of correct users, before being used for something bigger? Some kind of reckoning, like second coming of Christ etc. It does feel very religious altogether, not just the angels, but this whole ritualistic theme.
6. They ACTUALLY fly! That's how they can go between Heavens and the Pit. Is that a mutation? Ability? Blessing, Jinki, whatever? Are they even human? If they're angels, who is a god? I'm feeling the good parts of Fire Force here :3