Sorry for the delay. Work was cuh-razy this week. (City councilman got indicted, with all sorts of ensuing fallout.)
As for the revelation of who sent the Book of Ascendant Night to the doomed Sisters of the New Dawn, the name of the sender should be familiar to those of you who have read the Ptolus comic book series.
My theory is that, a century ago, he wasn't necessarily the head of House Vladaam (although he may have been), and saw an opportunity to chip away at the power of the good guys. For a Palastani nobleman, giving a book to a courier and sending it to the other end of the Tarsisian Empire isn't particularly difficult. By 721 IA, he's probably forgotten it ever happened. And besides, what could anyone do, if they found out?
At this point, the player characters haven't headed to Ptolus -- they have their hands full with the events in Midwood -- but if there's a sequel campaign, it will take them that direction, for various reasons, and I expect that Emmerson and company won't be quick to forget the name Vladaam.