Thoughts on Origins of the Library: You write a lot here without actually saying anything. I like the idea of "The Library began when the first human looked up at the night and wondered what lay beyond the stars", but it needs to be elaborated on more and the rest of this is really just long metaphors that all boil down to the same thought- "the Library be grand yo". That's not much to go on. I'm also not seeing any compilation or annotation here. Your writing/style itself is pretty good though.
Thoughts on Starlight etc.:
still as an unwound watch
This simile falls flat. It doesn't instantly conjure up an image in my head.
The starlight reflects off of the metal and stone of its streets and buildings, which have remained pristine over the years through some arcane means.
Two things: You begin the sentence before this with "the" too, and the one after it. It's clunky. Also, saying "through some arcane means" adds nothing to the sentence. I would cut it.
The repetition in the last two paragraphs is grating.
This really, really needs to be longer to have any sort of impact.
Thoughts on Glorious: Your habit for repetition is on full display here and really grating. You should be repeating yourself as a constant thing. It should be used carefully to increase the impact of a sentence. Length… same as the other. You're trying to capture a single emotional moment in a few paragraphs and it doesn't. As Vivax would probably tell you, this needs more character than just a generic warrior, and the transition from "this is glorious" to "this is disgusting" is a jarring one. I think it would be best to single out a specific event that made him realize "oh fuck I'm a monster", instead of him just going "oh wait i'm killing people huh".