How would you do it?
In my current project, magic is a rare thing that has practically become myth. I have one character, though not yet revealed, that has some magic, most of which focuses on the controlling of light (and therefore shadow), and can't really be lethal.
Where my problem comes is that I plan to introduce one character after a while, a knight from the impoverished empire to the north of my main setting. Not just any knight, he has sought out information on the secret arts and has come upon magic of blood and something else. I am seeing him as being able to drain the life force of his foes if they have so much as an open papercut, and using the remaining energy in even dead bodies for his own purposes - or even animating those dead and controlling them with his mind (Not necromancy - he'll need to concentrate on their every action). He'll also be able to take control of people. The other part is a little harder to classify, but the closest I could get is 'spirit', though this fits my world not at all. I see alot of bluish effects there.
The thing is, most of the magic in my world is very subtle, and I think his is a little less so. Should I tone him down, or will up-front, in your face magic where it isn't otherwise found strengthen him as a unique character, and, in fact, as a protagonist? Yes, that's right, his magic seems like it belongs to a villain, and though he's far from a saint he's not evil. No one's 100% evil in my story, though, they all have moral complexity.
How would you deal with magic in a world where magic is as rare as, say, North Americans who speak Swahili. And then rarer still.