Ex Cathedra is the seventh level in Marathon 2: Durandal. It is the first level of Garrison, the third chapter of the game. The southeast part of the level is a maze of twisting watery passages where you have to destroy a Pfhor power supply. After that's done, you can enter the temple in the northwest part of the map that is used by the Pfhor, according to Durandal, "in their pathetically boring religion". Inside the temple, Durandal will give you a virus chip to install in a nearby location.
There are three pattern buffers in this level. One is found at the start of the level, just inside the entrance to the temple. The second one is found in the the water-filled southeast area, next to the Pfhor power supply that must be destroyed. The third pattern buffer is found inside the temple, on the north side of the upper floor.
There is a 1x shield recharger on the west wall of the temple. A 2x shield recharger is found inside the temple; it can only be accessed near the end of the level, once the temple doors are open.
At the entrance to the temple, use the pattern buffer, then go northwest to find the 1x shield recharger. If you go outside further to the west, then south, you'll find some ammo and an oxygen canister on a ledge overlooking the starting location.
Still outside, go north and make your way around the north side of the temple, then go back south to the starting terminal. To the east, you'll find a room with a square water pool. In the southeast corner you'll find an entrance to an underwater maze. There are two exits to this maze: one is a long tunnel leading west to some oxygen canisters (quite useful, as there are no oxygen wall panels in this level) and an elevator leading up to the square pool. The other exit to the maze is a southbound tunnel leading to an outdoor water-filled area with submerged ledges you can stand on. In the middle of this area, to the northwest of the entrance, you'll find a door with the Pfhor power supply circuits behind it. It's at the encircled location marked "A" on the map. Punch the circuits and don't forget to use the pattern buffer there as well.
From the pattern buffer, go around to the northwest part of this watery area to find a passage just above the waterline running westwards. A secret door in the north wall of this passage will take you back to the temple. The temple's doors are now open, so go inside and kill the enemies. A 2x shield recharger is located in a niche here, and Durandal will teleport a chip onto the main altar for you to pick up. Take the west elevator up, then go north and up another elevator to reach the temple's upper floor. There's a pattern buffer here.
Go back outside to the square pool room to the east of the temple. Now go north and fight through a few rooms to reach a circular pool. Jump in; you'll find the panel where you need to insert the chip at the north end of a short underwater tunnel.
Now go back to the pattern buffer room on the upper floor of the temple. Take the east elevator down to reach the final room of the level, where the exit teleporter will take you to Nuke And Pave.
There's a small secondary temple entrance to the north of the temple. The east wall of the entrance room here is a secret door (see location C on the map). You'll find an Alien Weapon behind it, as well as a button that opens the temple doors. You can go straight to this button from the start of the level to skip the long detour through the water maze.
Near the end of the water maze, at map location D, there's a hidden door that allows you to reach the Pfhor power source a bit earlier.
The first terminal is a message from Durandal, who has created a virus to attack the Pfhor defense systems through exposed communication lines. He will teleport the virus onto the temple's main altar, where you can retrieve it and insert it into the system. He tells you the Pfhor will likely close off the temple, and advises you to destroy the doors' power supply.
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 you must press the attack before they recover, sending you off to Nuke And Pave.
- When this map is opened in a map editor, a written message can be found outside the bounds of the level. It reads, "The NAR". The Nar are an alien race mentioned in the terminals but never seen in-game.
Marathon 2: Durandal - Level 7: Ex Cathedra