Re: Designing Your Magic System
I still think the best, most useful, generic description of what magic is & how it works is the one given in Stackpole's Once A Hero.
Unfortunately I lost my copy of the book years ago, & never think to look for it when I have money to spend on non-gaming eBooks, so I don't actually remember how it went...
(I think it was along the lines of Magic being the manipulation of Energy, Time, & Probability by Willpower & Skill).