When worldbuilding for fantasy novels, it is a good idea to figure out the magic system at least by the second draft, or so I would think. Like with many aspects of the fantasy world, there are many things to consider when adding a magic system. And the two novels I really need to worldbuild both have magic but the systems are very different, which is important because the stories are very different so I wouldn't want the magic to be the same.
The steampunk-inspired one (needs a title so I can stop calling it that) has a fey main character and the magic is elemental. The elements in the story are water, fire, earth, wood and metal. Wood is the main characters element, so he can't control the others like he can control wood. Limits are good to have because having a character who is all powerful with magic can make the character a little boring and unrealistic. His magic is part of his trade, because he is a wood fey he loves to travel and gets work on a wood airship because he can magically fix the ship which is much easier when flying than having someone fix the ship by hand. But give him metal and he can't do anything with it, can't even really use metal weapons.
The epic fantasy series is very different. Sure, it has a non-human main character that does magic, only instead of a fey it's an elf. But there is more than one elf and not all elves are capable of doing magic, that they are aware of at least. The other elf will eventually be able to do minor magic because all of the elves have a certain level of magic abilities but most are minimal. Only one type has strong abilities and most of those don't exist anymore in the series as they were killed out of fear. The one main character does have those abilities but it's not easy for him, having to hide his abilities because of those that would act out of fear against him. And while he is technically very strong in his magic he is very careful about using it to the point of being self-conscious about what he can do. I'm still working on figuring out this magic system since it's not an elemental type.
Here is some thoughts on building magic systems that I found on a blog that has advice from Holly Black. These are six questions (posted here) to help with the developing of a magic system.
1. Who has it?
2. What does it do?
3. How do you make it happen?
4. How is user affected?
5. How is world affected?
6. How are magic users grouped & perceived?
These are questions I am considering when it comes to the magic systems that I am creating. So, what about you? Does your story have a magic system? What have you done to develop the magic system?