I was talking to my son the other day about the BAT and the apocalypses.
He suggested that maybe all of the various apocalypses either have happened already, or will. Meaning that perhaps Ragnarok has occurred and the Christians Apocalypse is next, or something like that.
It could relate to the changing of the guard at the Outer Gates.
I do find this quote from Gard to be interesting in relation to this:
"Einherjar. Give them a little sip of renewed mortality, and four thousand years of discipline go right out the window."
1. Viking mythology simply does not go back to 2,000 B.C. Earliest records of Odin (or Woden, at the time) are Germanic in origin, dating to Julius Caesar's
Commentary on the Gallic War, circa 1 B.C., where he was actually referred to as Mercury, because Romans were not particularly interested in understanding their enemies' religion. We're talking Bronze Age, predating proto-Nordic migration (which is currently estimated somewhere around 1,000 BC, if I remember). Odin was much, much, much, much older than Viking/Gallic culture. This is around the time Stonehenge was completed (anywhere from 3,000-2,000 B.C.. The stones themselves have been dated to somewhere between 2,400-2,200 BC, but there are so many conflicting reports, it's stupid, and there is some evidence that activity around the site involved rituals and constructions that date to
8,000 B.C., but that's a discussion for somewhere else).
Anyway, this supports Kringle/Vaderrung's intimations that he's changed a lot over the years, and may be something of a Time Abyss. Towards the end of the Nordic Neolithic Period (around 3,000-2,000 BC, right in our time frame), there is a ton of evidence that suggests new tribes of proto-Indo-Europeans moved into the region, which changed the language, and promoted the so-called Battle Axe Culture. In short, precisely the kind of people who would like Odin (or proto-Odin) as a deity. I posit that, in the Dresden Files, these are the people who participated in the 1,200 BC Nordic migration to Gaul, and mixing the people changed their culture, mythology, and deities, to eventually give us Odin.
The above might've been a little in the weeds, but Nordic and Viking Culture was something of a study of mine once upon a time, and I found this relevant.
2. Why are they mortal now?
This suggests either they have already fulfilled their purpose, that Valhalla is gone, or that their purpose is about to be fulfilled. I lean towards the latter, because in all of the stories, the Einherjaren
lose.