I just finished re-reading the Backup short story. That's the Thomas pov one where we learn of the Oblivion War. In it, the bad guys are trying to get the White Council to publish a book of rituals. The White Council would do this because, as we learned in Blood Rites, if everyone is using ritual magic, the sponsor doesn't have enough juice to make each ritual effective and they all just kind of fizzle out. The reason the bad guys want the ritual book published is because it would spread word of their "[d]emons of such appetites and fury that only the way mortals in some parts of the world survived them at all was with the help of some of those early gods." So demons who were worse than gods who favored human sacrifice.
These demons bear a resemblance to Lovecraftian horrors. Outsiders are somehow connected to those same horrors. It seems reasonable to assume, even if incorrectly, that the Oblivion War is aimed first at Outsiders, or that Outsiders are the results of successes of the Oblivion War. We have good reason to suspect that the Oblivion War has broader aims than these ancient demons because Thomas specifically says the fae were targets saved by the G-men, Gutenberg and the Brothers Grimm.
The only ritual we know anything about is the one from Blood Rites that was powered by He Who Walks Behind, the most powerful Walker of the Outsiders.
What if the reason that ritual spells fizzle out isn't because the sponsor has run out of juice, but because the sponsor has achieved its goal of anchoring itself to reality? What if every time the White Council publishes one of these ritual books, they are doing the work of the Venators' enemies in the Oblivion War?