I'll go ahead and give you a grammarcheck as promised.Grammarcheck
Bold are corrections made within the text. Other formats (underline, italics, color) are explained after the quote!
Fog blanketed the ground, concealing the advancing army. Alexis stood in front of the gates of the Academy of Mage. She stood tall and radiated the power of her heritage. Her eyes were a deep blue, burning like cobalt flames. On her back perched two red and black wings. She stood with an army behind her, preparing to rid the world of one of two most powerful mages of the current century. She had a staff strapped to a black cloak that sported her symbol, a half human and half demonic. Her fingers curled, [no comma] tightly around the lock on the magically fortified gates and yanked hard, shattering it. She let it fall, thinking, satisfied, ‘It’s time you’ve paid for your crimes, Allen Quing.’
Italicized: I've noticed already there's not much variety when starting sentences. Notice how many she-stoods you have alone! Besides that, each sentence starts with either "she" or "her," and that gets very repetitive. Try to work with some variety. One way to help this is to lay off the descriptions. I'll admit right now that I absolutely love how you described some of her aspects. Unfortunately, they're buried behind some of the annoying repetition.
In addition, so much description bogs down the beginning of your piece. It gets tiresome, and it's probably best, in this case, to start with fighting. Skip all this and get right into battle. That's much more interesting. Just a suggestion though!
Underlined: More repetition. This is one that stands out to me probably because Papa Hut was always quick to point it out to me. Anyway. Lots of of-thes, especially when they're in the same sentence. Try to shorten those sentences to get rid of the.
Red: The description was weird here. I still don't know what the symbol looks like. At this point though, it's probably not important to identify. Do that later when things slow down and we're introducing characters in a much quieter setting.
Orange: The "thinking, satisfied" was weird. Just choose one! I'd pick "thinking" since the dialogue after it should sound satisfied already.
“For the Freedom of the Halflings!!!!!”
Eek! It's not proper grammar to use all those exclamation points. Just one is necessary!
With eyes blazing, [<== comma] she took to the air and swooped into the school. She took the route to the Headmaster’s office. She could hear the shouts of her comrades behind her as she skidded and turned left, her left hand pulling free her staff. She could feel her magic pushing, fighting to be unleashed.
Italicized: So each sentence has to start with a subject followed by a verb. That's what consists of a standard English sentence, and it's how it should start every time. In this sentence, if we start with these transition phrases like "with eyes blazing," all you have to do is put a comma after it. That's one job the comma has! It separates phrases from the sentence itself. Take out the phrases, and the sentence should still have a subject and verb and the sentence should still make sense. So that's how that works!
Underlined: Each sentence starts with the same word in this paragraph. Variety! Switch up the sentences a bit!
As she reached the door to the headmaster’s office, [<== comma] a gust of wind sent her flying back. Crashing to the ground, she saw Allen standing there. He held his own staff, his eyes a bright red. The look of hatred and greed in them disgusted her as he hissed, “I will gain my immortality!! All I need is you!”
Italicized: Just want to praise you for getting it right here! You have the comma properly after the phrase! In the previous sentence, you didn't. So be sure to plug that one in.
Underlined: Just one exclamation point! The words themselves plus the character should make the sentence as dramatic as you want it.
Alexis stood up, her eyes flaming as she silently sealed the room from others, before she hissed, “Fat chance, Allen! I will beat you.”
Italicized: That's a huge phrase. Make another sentence or rephrase this one. I had to read it twice to understand the sentence, which is never a good sign. D:
He grinned, [no comma] avariciously, “Your soul will become mine! I will have it!” With that, [<== comma] he lunged, sending a wave of vines at her. She quickly dodged them and sent her own attack back.
Italicized: You don't need a comma before most adverbs if at all. It's just describing the grin, so why break it off?
The two continued this elegant dance of attacks back and forth, dodging and striking. The rhythm was set, neither of them really landing a good hit. Soon, [<== comma][ however, [<== comma] things began to get heated. Alexis unleashed her power, [<== comma!] and the castle began to shake, [period instead] with a lunge she attacked. The staff sliced Allen’s arm, leaving a large gash from his elbow to his wrist. With a roar of rage, his magic reacted, slamming into her head, sending her crashing to the floor once more. She laid there, [<==comma] dazed, the blow knocking all the air out of her lungs.
Italicized: Not sure if this is an appropriate word. From what you told me in the previous paragraph, it didn't sound elegant at all. Either choose a different word, just get rid of the word, or describe the battle beforehand to be more elegant. xD
Underlined: "However" is one of those transition words that automatically tell you it needs a comma. Just like the phrases I mentioned before, it should be comma'd out of the sentence. ;D
Red: A couple things here. First of all, the comma joined two independent sentences. That's a very common mistake, for some reason. xD Don't do it! Periods are your friends. Don't give commas the satisfaction. :[
The second thing is the comma I added in the sentence. Another common mistake is not knowing when to put a comma with those conjunction words like "and". Here's the trick: If there are complete sentences on both sides of the "and" (that is, a subject and verb on both sides), then you need a comma. In your case, you have "Alexis unleashed her power" and "the castle began to shake". Both are independent sentences with subjects and verbs in each. Therefore, you need that comma to separate them since you used "and"!
Orange: Two phrases here, and that just makes the sentence longer than it has to be. Shorten it by deleting one. Or just rewrite it to make it read more smoothly.
Green: Just like the orange. Two phrases. Choose one or rewrite! It gets longer and irritating to read, which isn't a good thing. D:
As she struggled tobreathbreathe, he took out a knife, driving it deep in her stomach. With a startled gasp of pain, she kicked him hard in the face, desperately to get away. Yanking the knife out, with a cry of pain, she tossed it away, lodging it into the cracked stone walls.
Italicized: XD Silly goose! "breathe" is the verb you're looking for. "Breath" is just a noun.
Underlined: So this is where grammar can get complicated, believe it or not. You have a phrase of him taking out a knife, yet in the same sentence, he's driving that knife into her stomach. Eek! Two completely different actions occurring at the same time. Best pick one and go with it. Two sentences, if you want. But not in the same one like this.
Red: Too obvious. Just delete it. Of course she wants to get away! You'd want to say something if she actually enjoyed it. xD But it's too obvious if she wants to get away. Just get rid of this phrase.
Orange: There are a lot of parts in this sentence. An in all honesty, you could get away with deleting two of them. If you just had "she tossed it away, lodging it into the cracked stone walls," it would make more sense and read much more easily. Try separating this into two different sentences instead. Or just use my suggestion. You won't have to copyright. ;D
The two lunged at once, their magic finally fully unleashed. The pressure of the magic sent the castle crumbling.As they two fought, [<== comma] the hallway began to crack and fall around them. The ground caught fire, [<==comma] and the soldiers all stopped. They watched the fight, [b][no comma] in awe. Soon, [<== comma] however, [<== comma] their courage came back, [<== comma] and they fought once more. Swords and staffs clashed. The two paid no heed, continuing attacking and dodging.They were lost in their own struggle for power. Alexis' [<== apostrophe] hands gripped the red oak staff of Allen’s, [no comma] tightly in her grasp. Her fingers dug into the wood as she yanked it out of his hands; [comma instead] causing two things to happen. Alexis tossed the staff behind her somewhere amongst the rubble of the now fallen castle. He stumbled toward her, causing her to yank him to her face by the neck of his cloak.
Italicized: This is one of those obvious statements you could do without. Just delete it and continue with the fight.
Underlined: This is a common mistake that some people may even argue? But it's grammatically correct to put an apostrophe here. You correctly put an apostrophe-S at the end of Allen ("Allen's"), but because Alexis ends in an S, all you need is the apostrophe. That's also how you pronounce it to. xD It's weird!
Red: Now, there are a few ways of writing this. The first way is to just delete "causing two things to happen". Another way is to use a colon after that phrase. However, I don't think this is needed because the last sentence in this paragraph doesn't seem important enough to mention in a list of two things that happened. In fact, it's more of a cause-effect relationship between the two happenings. After the staff was tossed aside, she grabbed him by the collar. She didn't grab him by the collar because of yanking the staff from his hands. Maybe him falling into her arms due to her force in yanking the staff. Basically, just rewrite this whole bit.
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I'm afraid I don't have the time to finish this. However, I did mention a few points that you can, hopefully, apply to the rest of your novel. If you have any questions or requests, don't hesitate to come find me.
Keep writing!
Jabber, the One and Only!