Request for Editing Help

I've had a look at the first chapter of This Demon Lord Can't Live Through 99 Lives!, and I have to say it impresses me!

Below are my considerations on a (near) paragraph-by-paragraph basis.

Defaulting Wrote: A greater smile could not be seen throughout ~~the nine realms~~ The Nine Realms at this moment. Beaming brightly, jubilant at ~~his~~ the circumstances, was none other than Demon Lord Asura. Lightly clapping his hands, he announced [ consider moving this dialogue attribution to after the dialogue it attributes ], “Scribe! Record this monumental occasion ~~down~~!”

I would consider The Nine Realms to be a proper noun in context.

Additionally, as noted above, for dialogue attribution that follows some form of participle + adjective (consider beaming brightly, lightly clapping, etc.) structure, I would suggest moving it to after the dialogue. It can sound a little interrupting otherwise—although this is a matter of taste, and not a hard-and-fast error, or rule of mine.

Defaulting Wrote: A small imp scampered forth, pen and paper already in hand, ~~exclaiming~~ and exclaimed, “At once, your Lord [ this would more likely be "my Lord" ]! ~~What~~ How would you like this entry titled?”

I change "What would you" to "How would you" for the more standard collocation.

Defaulting Wrote: Immediately, the horrifying smile that would [ see consideration below ] terrify nations downturned into an equally horrific frown. Now in a pensive mood, the Demon Lord pondered. What would most exemplify and deify me? He snapped his fingers, ordering again, “Advisor! Give me your most appropriate thoughts on the matter!”

The use of the conditional regarding the smile is not wrong per se, but it implies that the Demon Lord's smiling does not currently terrify nations. If such was the intention, ignore this. If not, I would suggest "the horrifying smile that terrified nations". Again, I would move the action to after the dialogue (here, the being in a pensive mood).

Whether the Demon Lord's pondering should be treated as attribution and use a comma instead of a full stop ("the Demon Lord pondered, What would most exemplify and deify me?") is a personal choice. It could go either way. I leave it to stand.

Defaulting Wrote: This time, the tall, wiry figure of an aged demon strode forth. “Milord, I presume to imagine that only the most grandiose and awe-inspiring of titles would suffice?” He he ventured.

The "he ventured" is attribution of the dialogue, and should be treated as if it were comma-separated even in spite of the question mark ending the quote. It looks a little odd, but it's conventional.

Defaulting Wrote: A thin smile graced the Advisor’s face. “In that case, your Lordship, I humbly offer up the ~~title~~ suggestion of 'The Great Demon Lord Asura obtains the supreme treasure, the Golden Lotus!'”

I change title to suggestion to prevent confusion for your readers as to whether the Advisor means a title of nobility or the title of the entry. Context requires it to be the second one, but some readers might catch on this in their heads—I did the first time around. It's best to be cautious.

Defaulting Wrote: “Certainly, your Lordship!” a simpering voice cried out.

I would suggest attributing this simpering to one of the characters, otherwise it seems a little disembodied.

Defaulting Wrote: Once more, a grand, malevolent smile adorned the Demon Lord’s face. Future generations would surely sing the praises of the greatest Demon Lord to have conquered this land and acquired the fabled Golden Lotus. With this in mind, Asura turned his attention to the vaunted object itself.

Nice.

Defaulting Wrote: Nestled ~~between~~ within a mass of unassuming lily pads, the Golden Lotus would have remained nearly inconspicuous were it not for its vibrant golden glow. Clearly unnatural amongst its ~~roster of lotus~~ peers, the Golden Lotus seemed inordinately beautiful in the lake. Perhaps even more special about it still [ this is excessively leading; see below ] was the aura it radiated. Even as an immensely powerful Demon Lord at the peak of the world [ unusual collocation ], Asura still felt a special resonance deep within his soul. He was almost certain this was truly the mythical Golden Lotus.

Regarding the excessively leading comment, because of that sentence's order of arguments, we are introduced to the verb (and therefore the sentence's meaning) reasonably late into it, as far as sentences go. I would recommend "The aura it radiated was perhaps even more special still.".

Additionally, we are suddenly presented with the Golden Lotus and its lake and the first true semblance of scenery. It's very sudden. I would consider setting the scene a little before this, so readers aren't instantly catapulted into sensory overload.

Defaulting Wrote: “Of course, your Demonship!” the imp promptly responded, picking out a tablet from within his spatial storage bag. “Where should I begin?”

The comma here is not wrong, but the above is more standard. I would only use commas as you had for sentences whose meaning is split by the action. Here, I consider the imp to speak two complete, independent sentences, of isolated meanings.

Defaulting Wrote: “I don’t need to hear it all,” Asura waved impatiently. “Just summarize it.”

Same as the previous comment.

Defaulting Wrote: The imp furiously nodded, “Certainly! Your Lordship is wise! ~~Then let~~ Let me begin!”

This change I make purely for style, although it is minor enough.

Defaulting Wrote: “What?!” the Demon Lord yelled. “What am I looking at right now, then? And what beast? Scribe, I will wring your brains out if you have misled me this entire time.”

Ah, the interrobang. I would suggest avoiding it, but this means you must decide whether the interrobanged (...is that a word?) sentence is more an exclamation or question. Here, I consider it the former.

Defaulting Wrote: “N-no, no, no! I deeply apologize, your Demonship, I’ve read from the wrong tablet!” The imp profusely kowtowed~~, kneeling for forgiveness~~.

To kowtow is perhaps a little alien for some speakers, but it works. I would suggest it implies the kneeling enough that you could delete it, as above.

Defaulting Wrote: “Perhaps that would be for the best,” Asura derided with a cold snort.

Regarding the speech tags, you use a great variety of them. Some argue they should be kept simple, and others the opposite. I subscribe to simplicity myself, but consider if this forms part of your own style. If so, keep them as is. If not, perhaps only said, asked, and answered. This is more a personal choice than an editorial one.

Defaulting Wrote: “You are both courting death!” The Demon Lord screamed, snatching the tablets from both Scribe and Advisor. “Let me see what you’re even reading.”

I love the matter-of-fact interjections. Very dry humour.

Defaulting Wrote: The chilly reception of their stories startled both demons as they exchanged anxious glances. Asura was ~~stony-faced~~ stony faced as he parsed the text. In neither story was there any mention of a Golden Lotus to begin with. In fact, one would be ~~hard-pressed~~ hard pressed to find a tenable connection at all [ vague ]. Turning back to look at his subordinates, he snarled. [ keep next paragraph here ]

I correct the hyphens, although the markup makes that hard to see. I don't have access to proofing marks, to my great disappointment!

The "tenable connection" is to what, exactly? The relationship with the tablets' contents and reality? I would make this clearer.

Keep the immediately subsequent dialogue with the snarling. It's all the same section.

Defaulting Wrote: Although it was indeed better to be safe than sorry, it was also the early bird that got the worm. Asura had not traveled leagues just to have his objective plucked out from underneath his eyes [ odd collocation; consider "before his eyes" ]. It was still unbelievable that such a treasure remained unmolested in this rural, backwater country. Perhaps that was precisely why. No expert would go out of their way to this empty land bereft of qi or value.

I would avoid mentioning something like qi, which sounds like it might form a part of the story, in such an offhand way. If it's just a detail of this particular description, I would suggest it sounds too much like Chekhov's gun atop the mantle—readers might expect its return.

Defaulting Wrote: “Very well then,” He he decided. “Even if I cannot discern your origins, you are now mine, little lotus.”

For convention's sake.

Defaulting Wrote: The Demon Lord swept his hand, easily moving the precious plant into his innate spatial storage. However, he still felt unsure of himself. He resolved himself [ inelegant repetition of "himself" ] to thoroughly examine the curious object once he returned to his cave abode.

This is an oddly distanced action, the sweeping the Lotus into his spatial storage. Consider "The Demon Lord easily swept the precious plant into his innate spatial storage.". I consider the sweeping to imply the moving in one.

Defaulting Wrote: “Fine, then. ~~let~~ Let us go,” He he muttered, ripping open the nearby space and stepping through.

More convention.

Defaulting Wrote: “As your Lordship commands!” the imp squeaked out, scurrying past the Advisor to follow ~~him~~ his master through.

The him is ambiguous here. I take it to mean the imp scurries past the Advisor to follow immediately behind The Demon Lord via the ripping of space-fabric...

Defaulting Wrote: Said Advisor furrowed his brow as he promptly followed suit. The imp had beat him to the punch [ unusual collocation ].

...and my taking comes to truth!

Defaulting Wrote: “The air split in twain, sundered by the awesome power of Demon Lord Asura!” chirped a small demon. “Welcome back, your Demonship!”

More convention. Consider whether the stylistic bonus of twain is overruled by your readers' potential not knowing its meaning*, and being taken from the story as a result.

*Yes, "your readers' potential not knowing its meaning" is grammatical, and yes, it does look hideously prim and grammar-obnoxious, even to me.

Defaulting Wrote: “Yes, thank you, Herald. ~~you~~ You can stop blowing the horn now,” Asura responded.

The comma before Herald is the vocative comma, used to separate off the addressee of speech.

Defaulting Wrote: The Herald hurriedly nodded, scampering forward to bow before the Demon Lord. [ keep next paragraph with this one ]

The immediately following dialogue should be part of this paragraph, for the speaker hasn't changed.

Defaulting Wrote: Asura absentmindedly patted the small demon’s head, ruffling its hair. At least some of his servants seemed to be of use. [ keep next paragraph as well ]

Same applies here. We switch between the Herald and Asura, hence the paragraph break, but the action and dialogue should be together.

Defaulting Wrote: “Go have someone prepare my study. I will need it shortly. Other than that, do not slack off in your cultivation!” He he ordered. “I have hope for you forming your Demon Core in the next coming decades.”

Beware the comma splice, for it is evil.

Defaulting Wrote: As he watched the small figure disappear behind the turn of a corridor, ~~Asua~~ Asura sighed, turning [ inelegant repetition of "turn" ] to the two disappointments behind him.

Poor things.

Defaulting Wrote: “You two are quite lucky. Herald brightened my mood. Now, get out of my sight before you become even more of an eyesore,” He he spoke.

Here, you could also have "You two are quite lucky that Herald brightened my mood.", but I expect the above was your intention.

Defaulting Wrote: He had never encountered a treasure that showed such initiative. Even if he picked up the most basic flying sword off the markets and intended to make it his own, he still had to put in a token effort to refine it. To have a treasure that refined itself, for lack of ~~better terms~~ a better term, was unheard of. The Demon Lord felt that he could take this unprecedented situation to mean one of two things: this was a characteristic unique to a world-shaking treasure, or that this was hardly a treasure at all.

"For lack of better terms" is an unusual phrasing.

Defaulting Wrote: An optimistic man would hope for the former, but Demon Lord Asura was neither optimistic, nor man.

This comma placement might cause a few arguments. What you had previously (sans comma) was perfectly acceptable, but in my experience, I find the above reads a little better. You are free to disagree.

Defaulting Wrote: “Yes, Master. ~~your~~ Your study has been prepared as necessary,” a mechanical intonation responded from thin air.

Comma splice.

Defaulting Wrote: “Good. ~~take~~ Take me there now.”

Once more.

Defaulting Wrote: Instantly, Asura felt spatial warping as he allowed himself to be teleported by the Cave Spirit. A mere moment later, his surroundings instantly swapped from that of an extravagantly decorated hallway to ~~that of~~ a study of even more ~~superior~~ elaborate decor. Casually taking a seat behind his massive desk, he propped his hand up to look at the ~~still gleaming~~ still-gleaming Lotus.

I add a comma after the introductory "A mere moment later" for consistency's sake.

Describing decor as superior is odd in the mind. Here, superior implies a value judgement of some function, not necessarily of quality.

Defaulting Wrote: “Cave Spirit, activate all restrictions in this room and let everyone know that I am not to be disturbed,” he muttered.

More convention.

Defaulting Wrote: “Master, it’s done,” the ~~same~~ mechanical voice said.

Here, same does not necessarily imply anaphora, the reference to something forward in the text.

(For those of you poetry students, anaphora as used here has a strictly different meaning than what you are likely familiar with. It gets confusing, I know.)

Defaulting Wrote: “Great,” he mumbled, entranced by the undulations and changes emitting from the lotus. “I’m going to crack the secrets of this thing.”

Convention.

Defaulting Wrote: In his other, unoccupied hand, he began forming a razor-sharp scalpel of the purest demonic energy. It was time to conduct a few tests. A moment later, he resolutely stabbed at the lotus, intent at literally prying ~~open~~ the thing open.

I move the preposition for idiomatic reasons, but what you had was not wrong.

Speaking in general terms, I am impressed by your writing. I might consider utilising the senses a little more—describe what can be seen and heard—to set the scene. In some parts, it can feel a little like talking heads, although I would like to stress this is not a particularly serious or comprehension-impairing feeling.

Keep it up!