I'm imagining a world that has magic, with three magical levels. The first level is cantrips. Firelighting, for example, or lighting one's way with fist size balls of light.. Most people know simple little spells. They are too weak to cause any direct harm.
The second level of spells are known by professionals. Doctors, locksmiths, policemen, soldiers (at least at officer level) ect. Such spells can heal people or be used for harm/restraint.
The third level are known by very few and sane goverments which to keep it that way. Spells such as raising people from the dead who have recently died ect-a spell of this level is cast maybe once a decade.
Every spell has an opposite reaction. A healing spell to heal a broken leg will break the leg of someone on the other side of the world. Balls of light cause balls of darkness, heating spells make the icecaps grow,ect.Ironicly, harming spells end up healing someone somewhere.
What do you think the attitude would be to magic? Would you have some countries that just dump their magical ill-effects onto other countries? Countries suffering darkness by daylight, injuries ect? Would there be wars as a result? Or would magic be very strictly controled with harsh penalties for spell casters?