Even though I am not a sorcerer myself and all of those that remain are either dead or in hiding, I have been honored with the trust of several confidential and reliable sources. As such, I am certain the following information is entirely accurate.

Magic comes in several "pure" forms:
Innate Magic (also known as Wild Magic)
Elven Songs
Dwarven Earthspeak

Magic also comes in some "forbidden" forms:
Death Art
Blood Magic
Corruption Magic

Note that it is not in the nature of a historian to judge a certain type of magic as "pure" or "forbidden." These are simply the universally agreed-upon categories for types of magic, at least according to my sources who know far more about this than I.

Setting aside my historian hat and putting on my human one, I found myself cringing as I learned what the "forbidden" magics can do. I will leave interpretation up to the reader.