Can you explain the process that you go through to come up with your magic systems. So many fantasy books today have a "black box" type of magic system — in that you don't know how things happen but the caster just suddenly shoots a fireball out of his arse. Yours are in—depth and set out a very distinct give and take that the reader can understand.
All of your systems are unique, so again, how do you get to the point where you have a complete magic system that you feel is ready to put into a book. Since this is a discussion about Warbreaker, how specifically did you come up with biochroma?
I don't know if I can answer that question in the short space afforded by a discussion forum. But in general with my magic systems I'm looking for a variety of components. Most of them start with just an "Aha, there's something there!" moment in my head—either it's a plot hook or a conflict hook or a visual hook or something like that. I'm usually looking for something that does what I find exciting about magic, which is straddling the line between mysticism and science. And I'm looking for new ways to explore that. So when an interesting scientific concept occurs to me, and I can take it in the direction of "what if," that's something that I find fascinating.
For MISTBORN, for instance, telekinesis mixed with vector science was interesting to me. In WARBREAKER it was the concept of sympathetic magic—the idea that you can create something that's like something else and it will have power over that. I wanted to try and take it in a direction I hadn't seen before and blend that with the concept of animation, bringing inanimate objects to life. Those were interesting concepts because at one point people believed in both of these things as real forms of magic. They believed they could make it work. The myth of the golem goes way back, and the idea of sympathetic magic was around not too long ago—in fact there are still plenty who believe in it, in various forms of superstition.
So I look for a blend of concepts. I usually look for an interesting visual paradigm—something that will work in a way that helps the reader visualize the magic. I don't want it to all happen nebulously in the back of someone's head. (And speaking of rear-end fireballs, I do believe I read a webcomic where someone did that. It was Thog Infinitron...I guess it wasn't a fireball.) But anyway, I'm looking for something that you can see and follow the process of what the character's doing in a way that makes sense.
I find that if there's one thing to take away from this, limitations on magic are more interesting than the powers themselves. And so I'm always looking for interesting limitations, because that forces me to be creative and forces my characters to be creative with what they have.