For most of Something Wicked This Way Comes, magic is what Mr. Dark and his evil associates use. Yet magic becomes something much deeper than that. When Will's father kills the Witch with a smile, it becomes clear that magic is a part of life. It is a part of each of the book's major themes. There is a magic that comes with acceptance of self, and this is the magic that Charles Halloway uses to defeat the carnival. This magic comes from an inability to be deceived about what one really desires. There is also a magic that stems from common cause, and this is the magic of a community. A community that is truly intertwined may protect its members from evil because when someone desires something that may lead to their downfall there will be someone else there to help them. Finally, there is magic in age, specifically located in the carousel, but more generally in the fact that whatever age one feels oneself to be is a better approximation of one's real age than the number of years one has been alive.
Belief is a part of what makes magic real. When you do not believe in the magic it does not work. If you do not think that laughing will make things better, then odds are it will not. When Mr. Halloway stops believing in the power of the Witch, she loses her power. Halloway's laugh is a testament to how ridiculous her supposed powers are. People's beliefs carry tremendous power with them, and when you believe in something fervently it may have greater effects upon you then when you do not believe in it at all. The Mirror Maze loses all of its power over Mr. Halloway when he no longer believes that it is himself he is seeing.