Wow Cool idea...
did you also consider to follow the storyline of the books??
and for the magic stuf.. did you thougt about something like in the Starwars Jedi Knight games? that you can choose to give some stars to special skills and so grow in skills you want..
btw.. a cool storyline would be Rayek when he runs a way from the sunvillage and ends up at the palace...
or something like that..
you have a good posabillaty in training his skills in the trollcaves..
Just an idea..
I was thinkin.. you don't have to kill there.. and he has to use his powers.. and then you can go to this special training place where Ekuar is to train your powers.. and use them in the trollcaves..
wow.. I can already see it in my head..
maybe in such a game you better might use first person shooter (without the shoote. more like lara croft kinda)