Final Doom/MAP16: Deepest Reaches

Blue key


At the start of the level, you are in immediate danger with an imp attacking, and two other monsters. Run forward and turn left and attack the shotgun sergeant first. Once you collect his shotgun, you may turn your attention to the two imps.

Open the door, and you will see a lava pit with platforms to run across. There are some enemies in the pit that may sometimes block progress, including demons and cacodemons. If you fall into the pit, run to the southeast corner and collect a radiation suit for the best chance of survival. Next, press the switch on the right wall to raise the staircase back to the ledge. When you cross the pit, you can get the super-shotgun.

Go through the doorway at the other end of the lava pit, and watch for a sergeant on the right who will attack from behind. Continue to the right hand door, and you should see some stairs containing a chaingun and leading to a brown room.

This brown room is a monster arena that is activated by pressing a button in the center structure. Once the arena is opened, the outer walls to the south, west and north will open to reveal a large number of enemies behind windows. Take out the enemies slowly, by keeping cover behind walls - you may start from the Mancubus, or the enemies on the north. Once you cleared the initial enemies, you can collect the BFG to release two revenants and a rocket launcher. After clearing the room, press the switch on the left to open a door to the east. This leads to a watery section.

In the water, head to the east. You can check one of the northern passages for a chainsaw, and the southern passage for an invisibility (guarded by a Hell Knight). At the end of the eastern stairs, you will reach a room with a few enemies. There is also a teleporter that brings you to the blue key.

Orange key
With the blue key, return to the first junction south of the lava pit, and take the other passage.

In the first room, you will have staircases leading down, with a revenant hiding in the alcove between the stairs. You can use the rocket launcher here. Open the orange key gate to the north.

Climb up the steps, attacking targets in your way. When you reach the chasm, you will see imps and a revenant across the chasm. Depending on difficulty, you may also have two cacodemons and a pain elemental approaching far below in the chasm. Avoid jumping into the chasm before collecting the orange key, which may be found in the red-colored room to the west, and by continuing to the south. You will find the key found on a star-shaped pattern.

You should now return to the orange key door. If you fell into the chasm, or otherwise crossed into the northern half of the chasm, there are two exits that may be used to the left. The first is a lift that raises you to the start of the level, and the other is a secret marked by a lighter colored wall.

Finishing the map
The orange key gate is located to the east of the watery section. When you go through the gate and enter the final arena, you will unlock the exit.

If you fall into the center pit, you can use the lift on the left to get back up. You also have the option of going through the room to the left for the red key. To get the key, first press the switch on the north wall, and shoot the eastern face. Enter the opened doorway, and press the switch and run to the south platform. Press the switch visible above, and the other face door opens. Press the switch at the end of the second corridor, and you can return to the green room to press the final switch where you can get the red key. This key gives you access to ammo.

The fastest route to the exit is to use the door on the northern wall, and enter the teleporter. This returns you to the altar room, where you can press a switch, and walk down the stairs to the exit.

Secrets

 * 1) In the lava pit near the start of the level, there is a small gray floor in the pit. Standing on it causes it to raise itself to the alcove, which is the secret. While this gives you access to another part of the map, it provides no advantage.  You may also access this secret from the northern part of the map across the chasm, by a lit wall
 * 2) North of the lava pit, next to the door is a lit wall.  Open it to reveal a box of bullets.  The trigger for this secret is the thin doorway, and running across it might not trigger the secret.
 * 3) Past the orange key gate and up the stairs, you should see a branch to the right.  In the first turn of the branch, there is a wall with a different texture (which is hard to notice).  Open this secret door, and enter the room for two medikits and a BFG.
 * 4) In the red room that is reached after the orange key door, you should see a window.  This faces a wall that has an odd texture, and that doesn't block bullets.  Jump across, and you should get a plasma gun.  You may also use the back wall and collect a Megasphere.