The Power Of Four
In The Craft, Bonnie (Neve Campbell), Nancy (Fairuza Balk), and Rochelle (Rachel True) had already been practicing magic when the film starts, but they couldn’t really tap into their powers until they got a fourth member. Sarah (Robin Tunney) moves to LA, and the magic really starts. The film has many references to why four witches are needed. One reason is so that they can all represent a location: west, north, east, and south.
It’s also mentioned throughout the film that the number four correlates to the four major elements: water, fire, earth, and air. It seems that The Craft: Legacy will also continue this theme of the power of the four because in the trailer, it’s mentioned that when Lily (Cailee Spaeny) arrives, they have their fourth witch.