Hi Blue!
I think this reads very smoothly: almost like a second draft, rather than a first. The use of language is interesting and effective. It offers a sense of something ethereal, without getting too dreamy or esoteric. I mean, you are describing magic and magical effects, the language shouldn't be plain, and it is not.
As to your specific concerns, I'll take them in order.
The ending is not too abrupt. In fact, it is excellent. A short piece warrants a short conclusion and this one serves as a clear finish and yet also opens up the potential for more. By which I mean it gives the reader plenty of opportunity to speculate about what happens next. I would not change it.
I found the story to be a very enjoyable, quick read. As mentioned before, the text is efficient, without being clipped. Nor is it overwrought, which makes it a very accessible piece of work.
Magic? Here, perhaps, more is needed. I read the work before reading your concerns and then went back and read it again. During the first read, the manner of the magic system did not strike me as important. However, now that you have raised it, I can see that some clarity and depth might make this more interesting (but, to be clear, it works well enough as it is). But, I would add further that if you do develop it, don't get into the hows and whys; continue as you have already done with examples of its use.
Finally, I would say in this instance that characterisation is a matter of preference. It is a very short piece. You do not want to get bogged down with history and relationships but a word or two here or there can only help. I feel you have achieved that fairly well but it is possible readers with a greater interest in the why of this character's behaviour may want more. It is, without doubt, a story that leaves much unanswered but, it seems to me that that was the point.
I hope that helps. Feel free to quiz me further if anything doesn't make sense.
