Doom/E3M7: Limbo

This level is known for large sections where the ground can easily damage you. However, they are easily recognized by a red, blood-coloured ground. It is also norable for a series of teleports that are also needed to complete the level.

Blue key
Before you can use the teleports, or even unlock them, you need the blue key found to the left of the map.

At the start, there are a few sergents hiding behind the wall (and on hard, two more that are attacking). Kill them for the shotgun, and be sure to collect the ammo. When you enter the main room, the door behind the start opens, releasing cacodemons and revealing a backpack.

Head to the left exit and turn towards the south. There are two paths to reach the blue key from the circular room. The east path leads past two demons, while the southern path leads past an alcove containing green armor, and ammo. In either path, the blue key is located at the south-east corner. While grabbing the key lowers the bridges into the surrounding nukage moat, it is not much of an obstacle if you run across it.

There is also two switches on the southern wall to the left. One switch opens a secret (see below), while the other raises a bridge later in the map. This bridge is helpful but not required.

Red key
Return to the main central room, and head east. Take a left turn to see a room separated by the chasm. You can cross the bridge if you raised it, or take the stairs on either side. However, it's a one-way path. Enter the pit on the north, and grab one radiation suit.

The teleports in this section will return you to near the blue key area. Navigate the maze, heading to the west to reach the second room. Continue west, but turn south when you see the teleporter, to reach the red key. You can optionally open the door to the south and open all teleport doors.

Orange key and exit
With the teleports open, it's time to reach the exit. There are six teleports scattered throughout the level. To reach the exit, visit them in the following order:


 * 1) In the second room that's north of the start, enter the north-west teleporter.  This leads to a switch used to allow access to the orange key.  Note that you can run across the damaging floor to the staircase to reach they orange key, and that this section is technically optional.
 * 2) In the second room that's north of the star, enter the north-east teleporter.  This leads to the orange key, separated by a small gap that's filled after flipping the switch mentioned above.  You can technically run across the gap if you are fast enough.
 * 3) Found in the south-west corner of the map.  This leads to a switch that raises the bridge to the orange key door. This is technically optional, as it's possible to jump the gap.
 * 4) Found in the center of the map.  This leads to the orange key door.  When you open it, it reveals a switch that raises the bridge to the exit.
 * 5) Found on the western part of the map. Take a right turn, and approach the teleporter.  If you raised the bridge, you can head to the exit without issue.
 * 6) This final teleporter is found in the south-east corner of the amp.  It leads to a plasma gun, and is considered a secret.

Secrets

 * 1) BFG in the north-east corner. After you drop in, take a right turn, and head to the south.  The teleporter leads out of the area, but you would want the red key first.
 * 2) On the left of the map, the room with the star. This is opened by a switch found to the south; specifically the one in the nukage pit.  It contains a rocket launcher, a supercharge, as well as four cacodemons.
 * 3) In a hidden room south-east of the star. This is opened by walking through the loop to the south-east of this room.  It reveals blue armor, and a variety of monsters.
 * 4) The plasma gun, hound north-east of the exit.  To reach it, you need to go to the south-east corner of the map, flip the switch in the north-west passage, the switch in the south-east, and cross the bridge to the teleport.