When planning multiple eras in Mistborn, did you know, for example, all the metals and magic when you published The Final Empire? Or did you leave open areas that you hinted at so that you could later explore and fill in the magic?
Final Empire is an excellent example, because it established what my model became. I wrote Final Empire, having an idea, but not have the entire nin-book sequence plotted. Not even the three-book sequence. I wrote that one and said, "Let's just write the book and see if it works." This is generally what I like to, rather than planning out the whole series. The exception to this was Stormlight, which needed the entire series planned out first. But with Mistborn, I was able to write the first book having ideas of what I wanted to do, but just make that book right. And then I sat down and said, "All right. The first book worked. I have the characters where they work. Now let's build the series." And when I did that, I went into a lot more depth on the metals.
But I did still leave... I knew, basically, what the other metals were gonna do, but I didn't have the mechanics down. Because I wasn't sure if it was gonna work. Playing with time, and all the stuff in Feruchemy where I'm playing with Connection and things like that, these were all kind of fundamentals of the cosmere that I wasn't 100% sure how I wanted to play out. So I basically kinda did the "best of both worlds." I left those holes knowing what they were probably going to be. But I was very careful not to give too much about them in the original trilogy, just in case what I wanted to do didn't end up working.
And that's worked out pretty well. I did manage to finish writing books two and three of Mistborn before I released the first one, so I could make sure that the continuity on the narrative really worked. Still, there are some things that I would change. I was much younger as a writer back then. I think some of the stuff in the third book, though it clicks together, it doesn't click together quite as well as I wanted to. Ending of the first book, I've talked about before. But I'm pleased with that process. Though every author has to use a different method, I do suggest trying that one. It's worked very well both for Mistborn and for Skyward. Worked a little worse in Reckoners, to be honest. Because the first book, I did not deal with any multi-dimension stuff, but I built it in after. Wrote the first book, went back, made sure the first book worked, then I wrote book two and three. And I was never quite satisfied with how the interdimensionality worked in that series. I think the magic system ended up cutting a few too many corners. So, in that case, doing it from the get-go from book one, instead of writing book one and then building it, might have worked better. Book one remains the strongest of the Steelheart series, I feel, because of that reason.
Regardless, it's been an effective method. It worked very worked Mistborn. It worked very well for Mistborn Era 2. And it has worked really well in Skyward so far.