Doom/E1M5: Phobos Lab
This level ramps the difficulty up again, this time adding in lots of Spectres. To start with, a Spectre will cross the slime in front of you to attack you - kill it whilst it runs towards you. Once you've dealt with it, kill all the marines and Imps that follow it. To begin with, ignore the door in front of you, and the steps up next to it, and head down the corridor to the end. There will be two Spectres and a shotgun marine at the end - kill them. In order to gain access to the random opening on the wall beyond the slime once you emerge into the slime room, simply walk out onto the walkway and a bridge will rise up out of the slime. Turn around and go back to the steps up to the room straight ahead from where you entered the level.
Up here, you can turn left and snipe some of the various marines in the open section beyond the door that I told you not to open. This will make your life easier later on. Turn around and walk along the bridge in the slime room. At the end, kill the shotgun marine and Imps and grab the medikit and yellow keycard at the end of the corridor. From here, you can kill the enemies in the room beyond (assorted marines, Imps and a Demon or two). Turn around and go back to the slime room, but stay at this end of the bridge. To the left of the walkway you went on earlier you'll see the wall goes concave, and that the middle section of that wall is discoloured. Sprint down onto the slime and quickly run over to the wall and open it - this reveals a secret area with a couple of medikits, a rocket launcher, some rockets and a combat armour.
Walk to the end of the corridor and the wall will open automatically for you. Go to the door I told you that you shouldn't open, and open it. Kill off any remaining enemies out here (you won't have been able to snipe them all). Go through the yellow keycard door on the left-hand side of the outside section. You'll immediately be assailed by a load of assorted enemies. Kill them all, then go right. Interact with the wall below the high ledge to lower it, and get on. At the top, facing the way you got on the lift, open the right-hand wall. Inside, you can pick up some shotgun shells. Use the wall at the end of this chamber, and it'll open to reveal a larger area with a load of goodies including a Partial Invisibility Sphere. You have three choices here, as the path beyond the pentagram in the centre of the room leads to a blue-keycard-locked wall which you can't open yet. You can either go right from where you entered and go back out into the outside section. You can use the pentagram in the centre to return to the start of the level, or simplest of all, turn around and retrace your steps to the circular room.
Head down either of the staircases to the bottom. Once you get there, you'll be attacked from all sides by loads of enemies, so cut your way through to an open space and you can turn around and pick enemies off steadily. These enemies will come from the slime pit section at the bottom, and from two previously-closed off side rooms that you couldn't distinguish from the wall. Kill them all off and then grab the medikit in the alcove opposite the slime pit. You can then open the wall behind where the medikit was for a Radiation Suit. Turn around and cross the slime pit to the platform on the other side, and hit the switch. As you do, the two pillars will lower, revealing a shotgun marine and an Imp on each. Kill them off. You can then ride each pillar individually (you can step back on the switch platform to lower them again) to get the combat armour (ledge to the left of the switch when facing it) and box of bullets (to the right). Retrace your steps to the outside section.
Out here, you can run straight across from the yellow keycard door to a newly-opened section. Go up the stairs and go left. Kill all the enemies as you go, and make your way to the switch in the alcove in the dimming light room. Hit it, then head through. There are a lot of enemies down this dark tunnel, so kill them all. There will be a room overlooking the outside section at the end with a couple of Imps and Spectres in it; kill them and grab the blue keycard. Hit the switch to open a door down the stairs to outside. Head down and kill the Spectre at the bottom. You now have another choice - you can battle through what's beyond the blue keycard door down here, or you can take the sneaky way in which this walkthrough mentioned before was also blocked off by a blue keycard door. Go back to the circular room using the door to outside you just opened up and use the right-hand lift to get to the secret room. Go around the pentagram and turn the corner to find the secret entrance.
Go inside - this is why you're taking the secret entrance because this small area is really dark and disorientating and full of Spectres. If you quickly want to get to the exit, sprint left and hug the wall - once you reach a corner follow it around to find the door. If you want to clear this place out; you can do so. Blowing up the barrels near the marines and Spectres makes your life a lot easier. In addition, there is a secret area along the wall to the right of the secret entrance which leads to some goodies and a Light Amplification Visor which makes it a doddle to see in the dark room. Once the place is clear, head to the exit door. Open it, kill the three sneakily-placed Demons inside, and throw the switch to leave the level.
A total of 9 secrets:
- Before the bridge leading to the yellow key, open the wall marked with two barrels.
- When you jump off the bridge into the slime pit, open the secret door in the bottom-right corner.
- Behind the yellow key door to the west, open the secret door behind the medikit, for a radiation suit.
- Use the wall left of that radiation suite for a chainsaw.
- Use the wall behind the chainsaw for a supercharge. You need to touch the first step outside for the secret to count.
- Within the yellow gate area, go into the lift at the north-east corner, and open the secret door on the right, for a partial invisibility. (The other part of the secret is inaccessible until you have the blue key.
- In the area past the staircase (opened in they yellow key area), look for a secret door to the right of the entrance to the brown tunnel.
- In the darkened room behind the blue key gate, look along the southern wall.
- In the darkened room, open the secret door on the western area, and cross it. (You've already visited the area from the other side, but for full 100%, you need to cross this door.)
A quasi-secret exists in the darkened room. When you first enter, go forward into the alcove, and use the far wall. A door will open, but this doesn't register as a secret; it's only a shortcut.
An extra rocket launcher is in the north area. Also, health can be found in the western secret as well as scattered through the northern area.