I'm not at the end game quite yet but I've read somewhere (here, Larian forum, walkthrough, whatever) that magic cannot be used. I'm kind of wondering how my mage could possibly beat a boss with a dagger and light armor? Is it possible at all?

I guess I have another question since I'm rather stuck at the moment. I just cleared the Imp castle of all enemies up to a locked door where one goes from cavern type scenery back to castle type. I haven't seen a key anywhere that will open this door. I think the problem is my insistance at being pure mage - I only have lockpicking one and I never joined the thieves guild since I haven't found any magical equipment that allows pick pocketing (and, as I am told, learning thelock pick skill). Is there a key that I may have missed? Alternate way in if lock picking is too low? I'm at level 38 so, providing I can use magic, I should be ready to gather up the last of the council of six races and various mages :) and get to the end game.

Great! I couldn't understand why a mage would be forced to fight with weapons only - I'm sure you are correct at why I came to that conclusion. It was in a walkthrough (it took some time, but I found it) and, while I doubt you need to see it since I was wrong and it is old, here is the info: http://www.ign.com/faqs/2004/divine-divinity-walkthrough-529103