i'm sorry but it's a very good thing that neither Mount & Blade, Warband, With Fire & Sword, or Napoleonic Wars has magic. It would ruin the feeling of conquering all of calradia by building armies, getting lords on your side, acquiring equipment and the 'medieval' feel if you can shoot fire balls or heal your troops. I feel like it would make even less sense in Napoleonic Wars, because it's supposed to be historically in the Napoleonic Wars.
Don't get me wrong, I like magic in games. I love lightning in Skyrim, and all that stuff, because it's a fantasy world, but I just don't think it would fit in Mount & Blade.