TheDude,
As long as the mages are truly chosen at random, and each participant's list of mages is made public immediately after they've been randomly selected so that everyone finds out about it about the same time you do so that you don't get extra preparation time, and as long as no one uses the same spellbook twice, there should be no reason to worry about getting an unfair advantage. That being said, if you don't have an algorithm that can randomly assign lists of mages to players, simply roll a D12 four times per player, writing down every result, post the results, then shuffle all 12 mages into a deck and start drawing. Top mage card would be 1 and bottom would be 12. You could do this at the start of every tournament round. You might want to film yourself doing this, just to be sure.
It's not that I don't think you're trustworthy, but this should be really easy to do, and you might not be the only one who ever runs this league, and it's best if you set a precedent in order to prevent future organizers from cheating.
