If you’re going to write a fantasy story, you might consider including magic of some sort– something like necromancy, sorcery, the Force (also called telekinesis). But something like magic is fundamental to all fantasy stories. It is supernatural, and the very essence of fantasy. Since fantasy revolves around things like magic, almost nothing you think up immediately will be original. Telepathy, possession, elemental powers– everything has been done before, in so many different settings. In order to create anything that you can honestly call your own, you need to put some thought into it.
Firstly, bear in mind that nothing can be infallible. If your magic system can do anything, every magician you have is a perfect character– there is no suspense anymore. Even if omnipotence is restricted to the most powerful magicians, and the most powerful magician you have is your antagonist, you need a flaw. Otherwise, the villain is, obviously, omnipotent– who can stop him? Of course, you don’t want the flaw readily accessible, either. It’s a fine balance, but when you get it right, the magic system is much better off.
Think about restricting the system by what you need it to do in the beginning of the story. If you have a basic idea for a plot or a character, chances are you know what needs to happen to get the story moving.
For example, Bill wants a sandwich. What gets the plot moving? If the plot begins with him becoming hungry and going downstairs to get a sandwich, then his becoming hungry gets the plot moving. Therefore, if you want to add a magic system to this story, I would suggest you build it off either becoming hungry or making someone else become hungry. However, if the story begins with Bill finding that his refrigerator is empty of sandwich ingredients, forcing him to embark on a quest to find the Mayonnaise Spreader of the Apocalypse, the story would get moving when he fails to find sandwich ingredients. Therefore, you might want to base your magic system on making food disappear somehow, or emptying refrigerators– or even turning Bill’s mind so he doesn’t see the obvious fact that he doesn’t even like mayonnaise.
But by creating something like this that conveniently forces Bill into an epic saga we will tell and retell through the generations, we have created a contrivance. Just like a miniature Deus Ex Machina, contrivances are annoying. Thus, you want to create your magic system so complexly that the inciting incident makes perfect sense. Again, keep in mind the flaws– no single magic system should do too many things at once. You wouldn’t want a sentient Mayonnaise Spreader of the Apocalypse that could change the way Bill thinks about mayonnaise, as well as move things by telekinesis, as well as raise Bill’s great-grandfather from the dead. However, if the villain can plant irrational desires in people’s minds, perhaps he could force Bill to seek out the best spreader on earth, thereby leading him to one of the greatest sandwich making artifacts in history. Perhaps the villain can only plant desires as yet– perhaps acquiring the MSotA would give him the power he needs to destroy the world.
Always take into account the consequences of your magic system. Power can’t just appear; it always has to have a source. Many magic systems come from the magician’s own body. Others take power from different sources, like jewelry or precious stones. These sources can often serve as limits to a magician’s power, as they can only carry so many sources around with them. Also, take into account the laws of physics. Yes, if your magic system allows flight, it’s rather hard to include normal laws of gravity– but if you need flight, consider simply removing a certain law of physics, like gravity, for one person. Magic will never be completely within the bounds of science, but it can bend one law at a time.
Make your magic systems different. As I write different fantasy novels, I notice patterns in my magic systems. I quite like immortal beings, for one thing. (Thank you, Castaways of the Flying Dutchman.) I also quite like intangible beings that possess human minds. I also like talking inanimate objects or animals. I’ve managed to name each of these concepts differently every time I use them, but they are never completely separate from each other. That’s kind of a problem. Things need to be distinct. That doesn’t mean I can’t use immortal characters anymore– I just have to have a different way for them to get immortal, and different side effects. But perhaps I should cut down on immortality for now.
This has been the rather disjointed explanation of the creation of magic systems, as laid down by me. I know I missed a lot; please tell me.