Doom/E3M5: Unholy Cathedral
The unholy cathedral is known for its large central chamber, which at first glance map trap players within the chamber. However, the map is relativly open, allowing you to explore most of the map without restriction.
The first task is to collect the blue key, located at the northern edge of the map. You may choose among the western path to reach the northern section, to use the central region to teleport closer (to get out, choose the north-west teleporter, marked by a pulsing light) and approach from the east.
To open the northernmost chamber, walk between the two pillars marked with a diamond floor light. Flip the north-east switch in the northernmost chamber, and grab the key in the north-west alcove. You can collect anything else you want in this chamber.
The last task is to head to the exit. The scenic route is possible, but the fastest method is to take the teleport at the south-west corner of the room to reach the north-east room. Take the southern exit, and head to the blue skull key door on the left. The exit should be visible within that room.
If you just go for the basic completion, you'll miss out on the many features of the map:
- Central region: The central region is easy to enter, but if you don't know how to exit, you'll find yourself trying random exits. Each time you find a new route to teleport in, you'll open one of the four pillars (which count as a secret). The teleporter at the north-west corner (which is glowing slightly) teleports you outside to the north-east chamber. All other teleporters return you to the center. This central region is easy to get into, but isn't required to complete the map.
- Northeast section: The doors out of this section are one-way; you can only enter it from the central region. It is guarded by demons (facing away from you), and contains partial invisibility and a berserk pack.
- Northernmost room: In the northern part of the map, there is a small pillar containing a diamond-shaped light. Pass through it to open up this room. In here, there's three switches: The north-east switch lowers the blue skull key, the north-west switch lowers a chaingun, and the south-east opens the six side alcoves to reveal ammo, a medikit and a rocket launcher. The teleport in the south-west corner leads to the northeast room.
- Northwest room: In the northwest corner of the map, cross the trapezoid-shaped slime pit to open a gate to a damaging room.
- Western room: The western room is a small arena with six demons, but the door locks behind you. There is also a plasma gun here, and a supercharge. To exit, flip the switch in the western alcove.
- Exit: The exit is on the eastern side of the map
- BFG: Instead of heading to the exit, take the right-hand path. The door will close behind you as you walk past, and remain closed for a while. Attacking the sole imp in the room will alert a swarm of monsters which will teleport in from the center. The BFG is located in the small room to the right. To exit this area, flip the switch to the right of the door in the BFG room.
- From the starting location, take the left-most door, and open the secret door on the left wall. Around the corner and across the blood pit is light amplification goggles.
- On the western edge of the map, you can find a small arena-like area with demons, and a plasma gun.
- In the northern part of the map, Flip the switch in the bottom-right crusher. This opens the back of the six alcoves, one of which contains the rocket launcher (located in the middle alcove on the right)
- To reach the north-west portion of the map, you need to cross over what appears to be some water. This opens a door allowing you to proceed. The secret is located on the right-hand side of the room between the two blue markings, and reveals a radiation suit.
- In the northern part of the map in the left of the half-circle section, look for a secret door. This has no obvious marking, aside from a window on the other side. It reveals some ammunition that you can collect.
- Enter the central region from its southwest corner to open the western pillar.
- Enter the central region from its southeast corner to open the east pillar.
- Enter the central region from its northeast to open the north pillar.
- Enter the teleporter in the northwest part of the map to open the southern pillar. This reveals a yellow skull key.
- With a yellow skull key, open the secret wall on the eastern edge of the central area - it is to the right of the mysterious writing, and reveals a chainsaw and supercharge.