This is one of those lingering questions that we're all waiting excitedly to see what's revealed. I'm curious what everyone thinks will be revealed once the Vatican's basement is finally opened up.
Personally, and here me out here, I'm of the opinion/belief that there's a literal demon or two chained up in the basement and that's where all of this witchcraft and other evil "magic" crap the cabal practices comes from. If you think about it, it makes sense. Solomon summoned and bound 72 demons and then forced them to explain the inner workings of hell to him. So why wouldn't someone with more nefarious intents do something similar but extract knowledge on how to extend the human life/youth (Adrenochrome), manipulate the masses (Mass formation Hypnosis), create drugs that cause more problems than they solve (Pharmaceuticals), cause wars at the drop of a hat, etc. etc.
Plus, this lines up with the whole "Great Awakening" and Christian themes, as well as the prophesized mass resurgence of Christianity on a nationwide, and global scale by people like Kem Clement.
What else could cause people to turn back to God like we've never seen before, like undeniable, definitive proof of the existence of demons, the afterlife, and by extension, God, Jesus, The Holy, spirit, and Heaven?
I can't think of much else short of a literal miracle from God broadcast on a global scale. So that's my two cents on the topic. Of course I'm sure we'll find other things. Hordes of "lost artifacts" like nazi gold, lost books of the Bible, heck, we'll probably find the contents of the Library of Alexandria down there somewhere.
But I think the most earth shattering thing will be a literal demon or two chained up and bound in some esoteric ceremony that these people are using as a source of their knowledge. Afterall, we can't forget about that time that the Catholic Church's head exorcist, literally talked about the devil living in the Vatican can we?
Well I might have worded it a bit badly. I suppose I should say that we'll stumble on the evocation apparatus, and someone will undoubtedly summon it, which will get out and be exposed to the world at large, thus proving everything as I said in the original post.
Though the possibility of them literally having a demon in a meat suit chained up is also there. Either way, I'm fairly certain once the basement of the Vatican is opened up, we'll have definitive proof of demons, God, the afterlife, etc. And it's going to be a shock for A LOT of people.
Dude when it gets out, the world might turn into a science fiction novel/series where there are magic colleges devoting their time to demonology and using it against other nations.