Magic is pretty standard mechanically. Gesture at things and shoot fire at them because you're a wizard, 'arry.

In-universe, magicians are individuals touched by insanity who burn up their crazy ideas in order to fuel their magic. Some theorize that too much magic might set the universe off-balance, some think that its the mark of deities giving you their blessing, and yet more think that it's tied in some way to the four-and-fifty lost pieces of Sudoku. Magicians are loners, tend to not seek employment or governmental benefits, and their greatest weapon is always their minds. Necromancers, by contrast, tend to work in groups, live in cities, and lend their powers to the common cause. When you die, you can be assured that your friendly neighbourhood Mortician will preserve your body and soul for community service in a healthy and stimulating environment of manual labour. Necromancers tend to be social animals, work in a unionised guild, and their greatest weapon is their wit and charm.