I'll start with the quote.
"Still don't see what the fuss is about," The man said. "A fire would do. One person, in and out."
"You underestimate the Wayists," The woman said. "There are warriorborn among their number, too." Her dark eyes glittered. "Besides. A fire is not enough. A message must be sent"
The man grunted. "Seems foolish."
"We'll never destroy them while they remain in heaven. We must therefore draw them out."
Bridget blinked at that.
"Baiting the mistshark," the man said. "Sometimes that doesn't go the way you think."
Alright, so I think this along with the quote about the archangel is the overall plot of the whole series. So Cavendish is working with the army to start a war, and I believe the codex is important to that war but we're not sure how yet. However, I believe, with this quote, that how she went around starting the war is purely to gain the attention of the archangels and draw them out of wherever heaven is for the enemy to destroy them.
Her stealing the index was for the human vs human war but her slaughtering the wayists and burning all the knowledge was for the enemy vs angel war.
I'm not really sure if anyone has already posted about this but I've been doing my second read extremely slowly and I've picked up a lot of text that we missed the first time around that has been answering questions posed in the forum.
Anyways, anyone have any ideas or opinions or anything on this?