Doom 64

This is a weird secret, but to access Hectic (the final level), you must go to Level 1 (Staging Area). At the beginning you will see an exploding barrel. Don't shoot it. There are 10 of these barrels in this level. Shoot every barrel except for the one at the very start. Now, when you have done so, use the teleporter through the Blue Door, to get back to the very start.

Look behind you and you will see a door. Now go over to the last remaining barrel and shoot it. Now run through the door and look beside the blood stain that is on the ground. A teleporter will be there, be quick to get to the teleporter because it doesn't stay there for long.

This level can be accessed through the Holding Area. Near the end of the level, you will see 4 switches. Flick them in the following order: 3, 1, 2 and 4. The circular platforms ahead should now line up. Now go through the small door and get into the teleporter.

Now you will appear in line with the 4 circular platforms. Run across them and go into the red room. Kill the Nightmare Imp and exit the stage. This is a Secret Exit which will have you go straight to Outpost Omega. Be warned that you will only have the guns that you exited the Holding Area with.

This level can be accessed through the Altar Of Pain level. To get there, after grabbing the Yellow Key, simply jump to the platform with the Soulsphere on it. Now do not jump off this platform. Look at the map and you will notice that the platform you are standing on looks like an arrow. Turn in the direction that the arrow is facing. Now run into the wall exactly where the arrow is pointing. You will go straight through the wall.

Now be careful as a Baron Of Hell roams this area. Kill it and exit the stage. You will now be sent to The Lair level.

This level can be accessed through the Spawned Fear level. To get there, after going through the Yellow Door and walking up the steps, you will hear a door open. Quickly run back through the Yellow Door and turn left and then turn left again and enter the room there (the one where you faced 3 Hell Knights). You will see a small area with a teleporter exit in it. Run for it before it disappears and that is it.

You will now be taken straight to Level 31 In The Void. If you fail to make it to the teleporter, just repeat the steps above, there is no need to restart the level.

The Terraformer - CB92 NBPL SYL? JO27
Main Engineering - BXYH ?G41 6Z4J PJ?Z
Holding Area - CYCC MGPK X47G TS2B
Tech Center - CF3? PG6D S12Z PFKB
Alpha Quadrant - BXRO TH1F 52GG 7W?B
Research Lab - BBXW HLGS XB8F 4RKB
Final Outpost - FVV9 FL55 QGFV DWJB
Even Simpler - FFLB MQ6C VV1C PF1B