Ex Cathedra is the seventh level in Marathon 2: Durandal. It is the first level of Garrison, the third chapter of the game.
Synopsis
You have been teleported here from We're Everywhere. The first terminal is a message from Durandal, who has created a virus to attack the Pfhor's defense systems through exposed communication lines. He is going to send you to the temple where the lines are exposed, and will teleport the virus onto the main altar, where you can retrieve it and insert it into the system. He tells you to destroy the doors' power supply after you've inserted the virus, as the Pfhor will likely try to lock you in underwater.
The second terminal is another message from Durandal, who reports that the virus is working as planned, and that the Pfhor's defense drones have gone berserk, causing panic in the remaining defenses. He tells you that we must press the attack before they recover, and you are teleported to Nuke And Pave.
List of Terminals 
- X-nil 37.9@cjl1//vck3
- e.thra 3-cab<783.7*78>
Secrets
- 'Outside' the temple, there is a stairway that will take you near where you started and a small stash of ammo.
- In the 'minor' temple entrance (it's a small octagonal room), there is a secret door that opens across from the entrance that contains an alien weapon and a switch that will open the temple to you without having to complete most of the rest of the level, including the water maze.
- In the water maze, as you approach its end, there will be a Fl'ickta hiding in a short hall that ends with a spinning rotor on the ground. Behind this wall is a secret door that leads to a secluded spot in the water-filled area which can also be used as a quick escape route.
Sources
Marathon 2: Durandal - Level 7: Ex Cathedra