Voodoo was a mystical practice that was believed to be able to enable the user to harm people or things by harming representations of them. This was believed in several cultures on Earth, and was also mastered by the Pain Casters on Vulcan. Count Dressler mastered the practice and began using it to attack Earth in the 23rd century, until he was stopped by the crew of the USS Enterprise. (TOS comic: "The Voodoo Planet")