In the Dresden Files, there's an effort known as the Oblivion War, to sever the connection that old gods and their ilk have to the mortal world. The way to do this is to remove these gods from mortal memory, because the mortals are their conduit into the physical world. (This makes it an incredibly hard war to document.) One of the common tasks of the Venatori, humanity's champions in the Oblivion War, is to destroy ritual books so that no budding sorcerer can call upon that particular deity.
Fortunately, spirits' memories don't serve as conduits like mortals do - fortunate, because they all would live forever without outside interference, and mutually prevent each others' disappearance. This means that the Archive, the repository of all mortal knowledge ever written down, doesn't directly block their objective, because the Archive isn't a mortal.
But Archive's mortal host can! What if the host, in a moment of mortal danger, decided to access all of the memories of all of the routes to power ever written down? Does a mortal suddenly know the lost knowledge that the Venatori have destroyed? Does that reopen the conduits for those beings?