Minor course correction.
Rather than there being two ancient letters, one from the hermit and the other from Bishop Augustine vouching for him, I'm going to have just one letter, supposedly written by Augustine, documenting his (Augustine's) private revelation (i.e., the vision) with many of the same details as I previously wrote them. Augustine, it seems, intended it to be found only after his death, so he addressed it to Rome, and left it for his assistant to eventually find. The assistant, a corporeal priest, sent the document unopened to Rome, where Satan, a corporeal cardinal and trusted member of the then pope's inner circle, receives it, shows it to the pope, and advises him that only a few trusted people should see it, discuss it, and report back to the pope as to what to do about it.
I'll then add a scene set at the beginning of the book of these trusted cardinals meeting and discussing it shortly after it is received, with Satan steering them toward recommending that the document be filed away for future "consideration" and that there be no copies of the document made, no mention of it to anyone else, no entries by the individual cardinals in their journals, and no other record of it whatsoever.
It then gets put away and eventually ends up in the Vatican Secret Archives, where it is conveniently found by Cardinal Song and one of his assistants (since Song is blind) over fifteen hundred years later. Song would have maneuvered himself into leading the ongoing Church effort to review and release Vatican archive records to the public. Satan could easily update the document several times during the 20th and early 21st century as he watches/steers events of the past century.
Of course, having the aforementioned scene of the ancient cardinals meeting and discussing the document will be impossible to make even remotely accurate for those times, so I'll have to settle for not getting anything too egregiously wrong. :-)
I probably won't even show the whole document in the book and simply have much of it discussed (both in the past and the present) by key characters + include carefully crafted quotes from the document to use as epigraphs at the tops of chapters, quoting Augustine. Each quote would, of course, be something Satan wrote, but with me (author of the novels) presenting it as quotes from Augustine, with no mention during the novel that the quotes are fake until the end of the book when De Rosa admits to Romano that the Augustinian document was part of the subterfuge.
Much simpler. And less like a data dump, although I'm still glad I wrote the two letters since I can use them to help steer the conversation and craft the quotes.
