The term "dark magic" is used to describe both black magic and gray magic, which is basically any type of magic that is not of a White Magic nature. White Magic is the true magic, the type most Wiccans and complementary Pagans choose to practice. It is magic that is positive and used mainly for the good of others, healing, love matters, spiritual growth, and beneficial transformations.
The opposite of white magic is, of course, black magic. Even those who possess a limited understanding of the Craft are aware that black magic deals with such negative things as curses, hexes, sticking pins into dolls, the summoning of demonic energies, the manipulation of others against their own free will, and basically any spell cast with a deliberate evil danger.
Black Magic is a false promise of power without cost and the idea of greedy wishes granted that lures the naïve into the darkness like flies to a spider's web. Jimmy Page of the very popular rock band of the 70's, was said to practice both white and black magic. Any study of the rock bands history shows a strong connection with black magic in the form of Aleister Crowley. The group not only read his materials but purchased his castle to record several of their albums. There were many evils that happened to the band including the death of Robert Plant's son (the nude boy in the film The Song Remains The Same) and the eventual motorcycle accident of John Bonham, their drummer, which ended his life as well as the band. There was a popular rumor with other musicians of the day that when Marc Bolan of TRex snubbed the band, he shortly thereafter, died in a tragic car accident. No one really knows, but after that accident there was no other "deep" rock band to stand in the way of Led Zepplin and the number one slots on the British and US music charts.
This threefold karmic retribution is known as the Threefold Law, or Law of Three. It works every time you do something bad, even if you do not believe in magic or Karma. The Threefold Law also works every time you do something good.
According to the book Earth Magic by Marion Weinstein, this is "The only law of Witchcraft.