First off, I want to tell you that your summary is very catching. It really draws you in, and that's one of the most crucial parts of a story.

I thought your pacing was fine. It was fast, but in an action-packed, suspenseful kind of way. I liked how you portrayed Severna's relationship with her mother. It's very tender and, I don't know, good.

This isn't really much of a critique (hah) but I also like Severna's name. It's original but not one of those crazy names that writers make up, as though they think the more complicated it is the more fantasy-oriented it is.

There were a few grammatical errors here and there, mostly just sentences that lack commas, so they tend to run on, and you also don't have many apostrophes where needed. I would also suggest adding a little more description - you're not in desperate need of it or anything like that, but you could give it a little more substance by adding some detail.

Anyway, I liked this story. I like its potential and I want to know exactly what Severna is going to do with this power.