[Fenris knows it means nothing to a caster so he doesn't take any comfort in it, but if this is a friend of Astarion's then he can give him the benefit of the doubt that he wasn't one of the mad magic users. Especially considering that magic in this Faerun wasn't all bad nor as easily corruptible as it is in Thedas.]

Yes, I have experience primarily with those who wield dark magics and makes deals with demons. While I knew one mage who was exemplary, he was only one of many terrible mages in my experience.