The last shift, while only a fraction of the predicted magnitude of this, was nearly five years prior and involved a brief "bump" between the realms of Earth and Neddel that actually generated a portal between the worlds with one side appearing in the Spirits' home library and the other appearing somewhere in New York City that only the human arch-mages knew of. The Spirits theorized that the location of this phenomenon was caused by the strong focus of magical energies contained within the library itself. That being the case, it seemed safe to assume that the portal's location on Earth had to be related to some equal or greater concentration of magic here.
This connection between the realms lasted but a few short months before the two separated. But now, a second far more destructive collision is being forecasted by the Spirits. The only details they know of as of yet is that the energy needed for the dreadful sorcery is being generated back on Earth.