; Date: May 14, 2017
In the preview trailer, while the Doctor, Nardole, and Bill, are walking down a Vatican hallway, the Doctor says "in darkness we are revealed" and is then shown pulling THAT BOOK out of his jacket. WTF? No explanation of course.
So.. did the Doctor return to The Library to fetch the DIARY he so carelessly left behind? Really, the secrets in that book, and he just left it on a ledge in such a public place. How irresponsible of the man.
And then the very last scene - briefly flashed - Missy.
Going by the background of that image, Missy is in this super-secret Vatican whose name is, if I heard correctly, The Hereticum. That archive would have all kinds of crazy secret arcane lore collected by the Roman Catholic Church over the last 1600+ years. They're reputed to have an extensive archive of this stuff that they're keeping out of public view. In this case that lore includes some kind of space-shifting creature that can reach through a stone door. The hand looks curiously like the monks we've been promised for later in the season.
Such a place would of course draw the attention of The Master (a.k.a. Missy). Missy probably shows up at the very end of the episode. No doubt there will be a cockamamie scheme involving some secret something-or-other the Vatican stored away.
No explanation of course. The word - well, here's what Wikipedia has to say: In Roman mythology, Veritas, meaning truth, was the goddess of truth, a daughter of Saturn and the mother of Virtus. It was believed that she hid in the bottom of a holy well because she was so elusive. Her image is shown as a young virgin dressed in white. Veritas is also the name given to the Roman virtue of truthfulness, which was considered one of the main virtues any good Roman should possess. In Greek mythology, Veritas is known as Aletheia (Ancient Greek: ἀλήθεια) and is the daughter of Zeus, or a creation of Prometheus. Veritas was often depicted nude, holding a hand mirror.
In the trailer - "The Veritas contains a Secret. Everyone who worked on the translation is now dead." Which reminds me of a Monty Python Flying Circus skit about a lethal joke that was weaponized in World War II.
Clearly they mean The Veritas is an ancient book of some kind.
And that those crazy-looking Monks are protecting The Veritas? We'll see soon enough.
Given the way the trailer cuts back and forth between The Veritas and The Vault, they must be connected?
As for The Pope appearing in another trailer? There doesn't appear to be any deep significance of anything, but it's very funny. Though, the first trailer does show The Doctor, a Cardinal, and some other people including The Pope, in the TARDIS console room.