Rudi explains Montival as "Mountain Valley" on p. 267 of Chapter Ten.
A few significant phrases have appeared in the text:
"game of thrones" (obvious);
"Chaos and Old Night..." (Milton);
"Principalities and powers..." (St Paul);
"'October first...'" (p. 286)
Why do I regard that date as significant? Maybe it isn't. I read the remainder of the page carefully but found no reference to lateness. See here.
In some sf, a superior technology intervenes and human beings must respond to events or circumstances beyond their understanding or control:
in Poul Anderson's The Avatar, an older civilization has distributed T-machines throughout the universe;
in SM Stirling's Lords of Creation books, a superior technology has terraformed Venus and Mars;
in Stirling's Nantucket-Emberverse series, some mysterious malevolent entities have caused the Event and the Change;
in Fred Hoyle's October The First Is Too Late, someone has generated a composite Earth with Greece in Socrates' period, France in World War I, Britain and Hawaii in 1966, the US apparently pre-1750 but really in the post-catastrophe fourth millennium, Mexico about 6966, Russia still uncivilized, China after the Sun has melted and fused the Terrestrial surface etc.
And sometimes it is natural events without any interventions by intelligent beings that change humanity or its circumstances, e.g.:
In The Days Of The Comet by HG Wells;
Brain Wave by Poul Anderson;
The Peshawar Lancers by SM Stirling.