As a Co-GM, I'll act my part. 

[url=http://typemoon.wikia.com/wiki/Magic]Here is a link directly related to how magic works in the Nasuverse[/url]

[url=http://typemoon.wikia.com/wiki/Magecraft]Here is another one[/url] 

While I have no real specifics right now that I am sure that I can give you and will be completely certain, I suggest we wait for Jelly to come up. (Late at night, that is) In the meanwhile, if you have anymore questions, I'll do my best to answer them. 

Also, about the Espers, it's as you say Grey, there are lots of them, but only 9 of them have nuke qualities.