Phew, that's a good bit of lore (:sun and kudos for including a few Ivalice races among the more traditional fantasy fare, I always love seeing them around). Is the magic system perhaps somewhat similar to Mage: the Ascension?

I seem to remember that it's all about true will-working in that game, but I'm fuzzy on the details... Anyway, maybe you aren't finished fleshing out the magic system, but some small explanation of its limits for the average character might be useful in the interim. Will PC Spirits really be as powerful as all that? Is a human mage doomed to mediocrity compared to an Elf or Faerie? If magic is so powerful and ubiquitous, why do the physical races still have importance in battle? Wouldn't a single powerful mage be able to defeat/kill scores of experienced Ronso or Bangaa warriors at once?