At the end of the last episode of Grimm,
the Zerstorer has killed basically the entire cast of the show, save Nick.
After killing the Zerstorer (somehow; it wasn't made very clear how), Nick realizes he can use the staff to bring the dead back to life, as the Zerstorer did. Before he can attempt this, however, a portal to the other place1 forms from the ashes of the Zerstorer, and he and the staff are dragged, apparently unwillingly, through it, emerging on the other side where the events caused by the emergence of the Zerstorer apparently have not happened.
What caused this? Was it Nick using the staff to restore his friends to life? Besides it being a very roundabout way of doing things, Nick seemed distinctly unwilling to be sucked into the portal. Was it some unconscious expression of his desires? A lack of ontological inertia from the death of the Zerstorer? What, exactly, was going on?