Hey ! I've been quite amazed this issue was never brought up before : Imagine you have a plot, a setting and two great ideas for a magic system ? How do you decide which one to use ? And what if you have several plots, settings, and magic systems ? How do you filter them to one or several book ? And if you have a great character and you wonder whether to add this trait or this power or to use this given power or character trait in the next book or someone else ? In short, what do you do with all the possibilities ?