Monk holes

I have returned to Neyi, to the ancient library of the monastery of the Tetrimon Order of Saint Jamyl. Baron Redwolfe speculates that bookshelf LXXIII may have been removed in old times by looters, but I wonder why they would have taken one specific entire bookshelf, rather than just ransack the place. 

Now, while they are not of much economic worth, the books that I am looking for are of historical importance. They describe a delicate part in the history of the Order of Saint Tetrimon. During the Moral Reforms, the order fought on the side of the rebellious Council of Apostles, against the Emperor. It is in this period that Grand Master Tetrimon IV is rumored to have hidden precious relics to keep them from falling in the hands of the Emperor. Two potential hiding places have previously come to my attention: the temple of God's Assuring Whisper, current location unknown, and the space city of Mezagorm, currently forbidden terrain.

However, if this library holds any lost records of that period, they could provide more clues as to the hiding place for these relics!

I find it suspicious that would be exactly these books that have gone missing. Perhaps they were moved to protect them or their contents? But then hopefully they were not moved very far, that would have been unwise in dangerous times. 

Some places, often monasteries, had "monk holes". These were ingeniously concealed hidden places built into the walls, where monks could flee to protect themselves during persecution or ransacking by, say, Blood Raiders. They were sometimes very cleverly disguised, for example a fake sewer. Such hiding places would be useful to hide books that the Tetrimon would not want to fall into the hands of Imperial troops.