The idea that there might be a force field or the like keeping beings from the nether world out of this one (most of the time) has to be derived from conventional physics - specifically, Maxwellian electrodynamics. The occult folkore of "vibrational energies" comes from the same source. The occult didn't try to establish its credentials as a pseudoscience until there was some real science to compete with.

Older folklore about demons and the walking dead is quite a lot scarier because more personal. They'll stomp all over our world whenever they damn well please, and if they follow a calendar, that's their concern and not something we can expect to understand in a quasi-physical way as being driven by barriers with variable permeability. Dorothy Carrington's books on the folklore of Corsica and Carlo Ginzburg writing about Italian supernatural belief systems give a good idea of what it felt like to live in a world populated by such things. Not fun at all. The dead and the angelic/demonic order were basically like the Mafia (which more or less replaced them). You want them off your back? - pay up, the natural order of things is not on your side.