The title is a perfect fit for the story, and it seems to have a matching name with the book that Mirea's father read to her as a child.
Your explanations are incredibly thorough and a bit poetic at times. It is very exciting to read, and your writing makes the story sound very action-packed. Your descriptions give your audience a clear idea of the setting and the characters, and it allows them to develop a detailed picture in their minds.
Minor Grammar Mistakes that I noticed:
Prologue: "...phantom like assassin's skilled in inflicting the most excruciating pain." Here, you used the word "assassin's" with an apostrophe, which should be used to indicate possession. Instead, you should write it as "assassins," to indicate that you are writing about assassins in plural form.
Prologue: "These sort of Kalasters lived in Sithrim however, and were almost never seen in Kasterlim." You may want to add a comma between "Sithrim" and "however" to add a proper pause within the sentence. Without it, the sentence seems too drawn out and it takes the audience a moment to sort it in their minds so that it flows more easily.
Prologue: "You could never be to careful it seemed in a time of war..." I believe you intended to write "You could never be too careful it seemed in a time of war..." as in you could never be overly careful.
Prologue: I noticed another mistake in the next paragraph regarding a too/to mistake: "...the day ushered in the blanket of black he so desperately clung too." In this case, the word "too" should be changed to "to."
Prologue: "...and would shield him from site." The word "site" often is used to refer to a location, but you could use the word "sight" to explain that the character was hiding from view (this is a very common misspelling).
Prologue: "'Your not a damn mouse.'" The correct form should be "you're," as in "you are."
Chapter 1: "'Forget my creations 6th birthday?'" Here, the word "creations" should contain an apostrophe, as it is used possessively.
Chapter 3: "After Mirea and her father had ate a simple morning's breakfast of..." The words used to describe when Mirea ate do not make much sense. This section could either be changed to "...and her father had eaten..." or "...and her father ate..." The words "had ate" do not work properly together.
Chapter 3: "The father decided didn't argue with the librarian, and instead slide all of the books into his leather shoulder bag after thanking her kindly." I suggest you recheck this section and make any necessary changes, as the words "decided didn't" do not work side by side with one another. Additionally, your story is written in past tense, but the word "slide" is in present tense. Be sure to go back and make sure that the tense is consistent throughout the story.
Chapter 4: "You're not some little Kasterling who needs tending too after some nightmare." Here, the word "too" should be changed to "to."
Something that I recommend you always double check is your use of "to" and "too." These are very easy mistakes to make, and I noticed it a few times within your writing. Be aware of this while writing, and make sure to correct it if you notice :)
A section that seemed unrealistic was in Chapter 1 where Mirea asked her father how he could afford her locket for her birthday. Generally, children at the age of 6 don't understand the value of money and they are quite absorbed in the gifts that they receive. Here, Mirea did not sound like a six-year-old, but more like an adult who was worried about spending too much.
The story holds a consistent pace, and it contains explanations that keep the audience hooked. The prologue nicely describes the setting, the different people, etc. that the story is based on, and the readers can vividly picture the story.
The story is packed with suspense, and the reader constantly wants to read about what comes next. The chapters are also uniquely named, and they briefly describe what is to come within the chapter. I do find the chapters to be a bit long, but they don't contain any irrelevant information. They all include many story details and they don't stray from the topic at hand.
The tone used in the story is very clear and consistent; I noticed that it was quite mysterious and gloomy as a whole. In my opinion, this benefited the story, and it helped the audience imagine how the characters were feeling and what the setting looked like. I also especially enjoyed reading Mirea's flashbacks, as they give the audience some information on her life when she was younger.
The characters are nicely composed and they are all quite realistic. For example, in Chapter 1, when Mirea turns six, her emotions are captured perfectly. When you wrote "she simply couldn't rest another minute now that she was a year older" , you nicely encompassed the attitude of a girl her age. Children are often excited by even the smallest events.
As the story continues, your readers experience it through Mirea's eyes eleven years later. Her character continues to become more developed as I read through the story. She is quite likable, relatable, and her shock when she discovers her magic is very believable. The story doesn't contain any forced actions or conversation, and it flows very nicely overall. The dialogue remains consistent throughout the story, and it fits the setting very nicely.
The story as a whole is extremely well-written and attention grasping! It is consistently action-packed and the characters and setting are very detailed.
*Analysis is based on the first 5 chapters