The cube is little more than a two-fold swastika: A spiritual square and a material square. A squared square, in other words.
The cube also contains the symbolism of the number six, since it has six sides. It also represents the "four corners" of the world, or the World Age as defined by the two equinoxes and two solstices and the attendant constellations rising helically thereon.
Our current World Age is the cusp between Pisces and Aquarius. To say it Biblically, the world (Pisces) is coming to an end (which is, of course, only a new beginning).