Easily one of the darkest forms of magic would be necromancy, which is the art of summoning and controlling the dead. Through necromancy, one could bring someone back to life, raise an army of zombies to do their bidding, or communicate with the souls of the deceased. However, like all magic, necromancy comes with a price. The darker the magic, the higher the price. One of the main characters in my fantasy books will be a practitioner of necromancy.