Realm of Chaos
E4M1 - Hell Beneath
Go out of the starting room and stand in the depression in front of the red door with your back to it. Opposite you there is a walkway which ends abruptly to the left. Jump into the slime and activate the end of the walkway, which will lower to reveal a short secret passage and some goodies.
The left wall of the secret passage is another secret door which reveals a room containing two teleporters. These can be used to get to the little niches from which sergeants were shooting you earlier.
Follow the path from the starting room, past the depression and into a room with two green torches set in small alcoves. Each end of this room has a 'mask' style switch which you should press.
The wall blocking your exit from this area of the level will now be lowered, so go through the gap and follow the path to the right. The building in the slime moat has an opening on its righthand side (as you first looked at it) which you should enter it by.
Once in the building, go up the steps and get the red skull-key which is on the left as you get to the top of the steps. Beware that as soon as you enter this room you will get bombarded with enemies teleporting in behind you.
On the opposite side of the room to the key are some dismembered limbs hanging from the ceiling. Behind these is a face on the wall which marks a hidden exit from this room (or alternatively, use the step in the main room of the building).
Go and open the red door which reveals a small room with imps hiding behind a metal 'wall'. Behind the wall is the blue skull-key.
Having collected the blue key, go back past the slime-moated building and open the blue door to reveal the exit.
The 2nd secret is actually kinda fun, though, so don't leave just yet...
As you face the metal 'wall' from the red door, there is a torch in a small alcove on the left hand end of it. If you press this torch, the metal wall will lower and you'll get a 'nice' surprise... Trust me. (The actual secret is only awarded when you walk over the logo that is revealed... but be careful ;)
Level 29 - The Living End
You start off by walking left around the outside of the map, killing things as you go, and you'll get to a room that has no way out. Moving to the corner of this room opens a door in the column behind you to which you press the key. This removes the barrier that is preventing you from reaching the hexagonal block with the baron firing his green stuff at you. Pressing the button on there will allow the floor to rise up to give you a three way exit to different doors. I took middle, left, right and this appears to work. The right passage isn't open until the button on the left is pressed and the door on the left isn't opened until you press the final button in the middle.
Phew. Going down the third passage reveals a vaguely circular room with the houses another of those green throwing dudes. Kill him and use the hidden door on the middle column to get access to the teleporter. This takes you to what I think of as the second phase.
This consists of three 'prongs' which you must press the buttons of (and use the teleporter on). To do this, you jump on to the right one, and look right from there. There is a Mancubus firing flames at you. Kill him, then run across the gap. Press the button, then run back across the gap. You'll end up in the lava, so run to the other end of the room and press the metal plated wall. It should lower the floor for you to get back to the start of this phase.
Now, starting with the left prong, run on to each and kill everyone, pressing the button at the end. Jump to the lava and get back to the start in the same way, then do the second, then the third prong. At the end of the third prong is a teleporter that takes you to the big central area of the map - the third phase.
Walk up the winding stairs, killing the eye thing and the lost souls, and then you'll reach the top. As you get there the centre should raise and the nice Mr I've-Got-A-Rocket-Launcher-For-An-Arm will decide that he doesn't like your life and attempt to remove it. Stop him from doing this by killing him first.
When you kill him, the level ends and you move on to the icon of sin. Which is a whole different kettle of fish.
Level 30 - Icon of Sin
First get all the weapons, health and ammo, and walk onto the transporter. Then run to the left, and press space when infront of the first platform. Then run to the right, and press space infront of the second platform. Then run to the middle, and press the switch. This will raise the pillar infront of the wall at the front.
Switch weapons to the rocket launcher, and run down to the base of the platform, and press 'space'. Get on the platform, and as it rises, wait until the top of your rocket launcher is in line with the demon's chin, and fire. The rocket should fire into the rectangle above the demon's head. Repeat this process about 4 or 5 times until the level is completed.