In my head I’ve been struggling to allow Nami to use magic to solve her problems as it seems like too easy of a way out. This podcast gives a good indication of why this is the case and how to overcome it.
Sanderson’s First Law: Your ability to solve conflict with your magic is directly proportional to how well your reader understands your magic system.
Your character can only explore the magic once you’ve laid down concrete rules so that the reader knows what’s going on. If you can just do anything, then there is no tension. If you know the mechanism beforehand, then the audience can put 2 + 2 together and say that this problem is going to be solved this way! Don’t just let the solution surface at the last moment or it will be a cheat.
Make the magic feel like a strength in your world. Make it believable.
Not all books have magic rules laid out. It depends on who’s perspective we see from. E.g. in Lord of the Rings, the characters solving the problems aren’t always those who use magic but when Éowyn kills the Witch King it is only after Tolkien has given us the 2 + 2 of how this can be done.
You can purposefully not explain the rules so that you’re tapping into the collective unconscious of being a fish out of water and feeling like you don’t understand how things work. This means that the hero is not going to be able to solve conflict with magic. Lord of the Rings is about normal people, the hobbits, trying to make their way in a magical world.
The Harry Potter series lies somewhere in between. It is not always rule based (which gives ease of access) but certain books have their own rules e.g. the rules of the time turner play a large part in The Prisoner of Azkaban, (portkeys, polyjuice potions, the floo network etc. in others) but elsewhere it is just like they’re shooting magical guns at each other.
What do you gain by explaining the rules? Knowing how the magic works is world building. Explaining the rules is a separate decision you need to make. In X-Men, the mutant gene is world building. The rules of what wolverine can do is explained so that he can play a role as a shield. Similarly Superman has certain rules and limits to what he can do (depending on which comic). Gandalf on the other hand is not explained but it is established that he can’t destroy the ring.
By explaining the rules early on, you can use magic to solve problems. You can make your character seem clever by manipulating the tools that you’ve given them in ways that you would not expect. Capture the imagination of your audience with your rules so that they can imagine what they themselves could do with them. This also allows for foreshadowing – the surprising yet inevitable.
Explaining the magic also gives you the opportunity to create an apprentice character. This can let you show off the magic system and create a sense of wonder. Let the audience think “wow this is cool, I can imagine myself doing it!”.
Once the rules get very solid then your start to appeal to another audience by taking on another form of the fantasy genre – hard fantasy.