https://docs.google.com/document/d/1i0YgvmoLolhXC4D_oL4W_x2lt_cnj-7tlmNj5avKjqY/edit?usp=sharing
Here ya'll go.

Good stuff. I like your writing style. Left a small note in the doc somewhere were I found a little grammatical error.

Hey there! I like to consider myself an amateur writer (emphasis on amateur, though), so I thought I’d throw in some of my advice.
Avoid using the same word twice in a sentence. For example, you used the word “academy” in the final sentence of the first paragraph. I don’t think you need to say “students of the academy” because the reader has already established that.
Watch out for a few punctuation things. In the second paragraph, when you said the “rest of the day was barely notable”, you followed it with “after the classes” with a comma in between. I’d suggest a full-stop instead.

Only extra advise is figure out where and where not commas should be used. Makes for easier reading.

It was an intense introduction, and your character’s voice is quite engaging which is great! I think, however, you could flesh it out a bit more.
It almost feels like the narrator is simply recounting, as opposed to living the story. I’d suggest using some literary devices: metaphor, simile, imagery - to help set the scene more for the reader so we can envision it in our heads, and also to become more engaged by the voice. Maybe a bit of sarcasm couldn’t hurt, or rhetorical question so that we engage with them more?
But yeah, that’s some advice from me! I hope it’s clear enough. :)

A part I think you should double-check:
“I hear tens of footsteps...”. Did you mean tens of thousands? It just felt clunky to me.

Maybe replace it with dozens?

@rosemagwin That’s what I would have opted for as well. :)

Thanks for the advice, some of the flaws are really obvious even to me. I didn't really refine the text everywhere, and the less flashy, more ordinary parts of the text are rather uninteresting, just because I suck at writing those. Also, to give reference: this is an excerpt from an important story event from a perspective of an outsider to the main story. This is mostly why it's short and focuses largely on the action parts of the narrative, and some major references are going to be missed by absolutely everyone unless I explain the whole thing.
But overall, thanks for suggestions :)

When writing in the first person, which is tough, something you have to consider is consistecy of eloquence. Use only the vocabulary and sentence complexity that same character would use in dialogue. Would this character actually say “slumbering” when speaking to another character? If not, simplify. You don’t want him to sound like a poet in his thoughts and a dolt when actually talking.

Interesting how the character notices the powerful wizard smile. Is there anything special about it? Sharp toothed? Menacing? Strangely amused or kind?
Also, I may have missed this but are they wizards, warlocks or sorcerers? Or a mixture?

I skimmed the beginning. I like what I see so far. I’m going to focus on pointing out some conventions and things like syntax that I feel could use cleaned or polished, then discuss other things as they come. The ideas seem solid so far though. Good work!

So, to respond about the ideas and context: The type of magic present in the world exists in a form of energy manipulation. It's not inherently elemental, and doesn't require any spellcasting other than concentration of thought and magical abilities/experience with them. Meaning if you can figure out a way to converge the energy into a physical form - a projection of a weapon for one - you can do so at any moment with a simple mental command. Mostly magic is used for combat with a very few exceptions - the more complex is the action, the more skill it takes. Simply put, even an ordinary soldier gifted with basic magical abilities can intuitively enhance himself to be faster and stronger. The line between pure mages and melee combatants is almost non-existent, both of them use a combination of "spells" and weapons. The only real differences are in styles and the primary way the magic is used - enchantment, summoning, and manipulation of energy. Enchantment would be empowering - cont.

- yourself to be stronger or faster, or making your weapon hit harder, summoning would be any attack that behaves on its own, or with minimal guidance, like creating a bunch of crystal spikes and launching those at the enemy, and direct manipulation would be creating a weapon out of pure energy, or launching projections of attacks.
Storywise, it's gonna be hard as shit to explain. Mostly, because this isn't an original world, instead it's pretty much fanfiction of the highest order. I basically made up a whole story based on everything that the original source didn't explain. And that includes making up the rules I just ranted about and about 10 new characters.

That’s really cool! I’m also (attempting to) write a story with similar elements, but mine is to do with faery magic and yeah. Best of luck!