Evil spells are considered devilry having originated from the devil.
Behind the scenes Edit
According to Roberta Wiliams when discussing KQ8 (see KQ8 development);
Earlier King's Quest's reflected my moods during those times: KQ3 was very dark, and it utilized lots of magic and magic spells with the basic idea of finding ingredients for "black magic" spells and then casting those spells. (Certain religious groups were upset with me over that one!