The Great Conflict
The tunnels are completely devoid of any light but fortunately you have a combination of sonar location, night vision and infrared all installed and readily available for you to use so this is nothing more than a trivial obstacle. It seems like these catacombs have not been accessed for some time. You find a primary access tunnel that takes you all the way to the underbelly of the monastery. As you get closer you begin to notice more signs of recent activity including some stored materials and even burials that may have occurred in the past year. Finally you come upon a door with light shown through the cracks indicating that it is the entrance to the populated section of the monastery. Upon entering this place you will encounter the faithful. Act accordingly.