[quote=@Ollumhammersong]
I'm still trying to work out magic in this. So do I just have dozen or so mages? Casually slinging fireballs or whatnot from horseback. Are people generally restricted to one kind of magic? 
[/quote]

People aren't restricted to one type of magic. However, They'd be more powerful if they did. It's a tradeoff between versatility and raw power.