Okay, let's do this!
Does this story sell the plot?
Mostly yes. I was a bit confused during the fire part, but I think the story conveys the plot well.
Does it make me want to know more?
To be honest, not really. I don't really like any of the characters that much so far, but maybe that will improve in future chapters. I also think that a lot of the "main" characters are really rude to people around them, so it is hard to be interested in them.
Does the dialogue fit together?
Mostly. There are a lot of ellipses, but that might just be your writing style. Also, a lot of the dialogue seems really childish. For example, I can't really imagine a king calling someone "Miss Thing."
Do I feel for Heiroe?
No. He is, for lack of a better word, an a**hole. I get that there is pressure on him to do well, but he treats everybody around him like garbage.
How does the action play out?
I like the idea of the "darkness," and, hear me out, it kind of reminds me of Tangled the series (my absolute favorite childhood TV show). Honestly, just because of this, this story gets like +10 rosiepoints.
However, it all feels a little ridiculous. They are supposedly trained all of their life yet Red's first thought as she's dangled over the monster's mouth is to lick its hand. Can she even reach its hand? She has a staff, why doesn't she use that? Things like this make the action seem a little impractical.
How do I feel about the side characters?
They're okay, just not memorable. I probably will like them more in future chapters, but for now, I am not particularly attached.