The Hazards and Secrets of Doom
The world of Doom conceals many wondrous secrets and deadly hazards. The marine should keep his eyes open for both of them, as the first will be helpful, while the second might harm or even destroy him. Traps are not that dangerous for the one who has been warned about their existence, just as secrets can be revealed by advice and guidance.
Hazards:
Exploding Barrels: Throughout UAC facilities are barrels that contain highly volatile liquids, such as fuel or toxic waste. While those barrels and the substances they contain are safe when stored throughout buildings, yet shooting at those barrels, disrupting their structural integrity, or suddenly increasing the substance temperature will result in a powerful explosion that will usually leave nothing from the barrel, and anyone that stood close to it when it went off. Though dangerous, such explosions can help if used wisely against the enemy.
Overheated/Radioactive Areas: There are certain areas within installations that might appear normal at first sight, but are actually overheated, or contaminated with deadly radiation. In both cases, walking through such areas will severely damage the health or kill anyone who is foolish enough to enter such areas. This hazard is, however, harmless if you wear a protective Radiation Shielding Suit.
Crushing Ceilings: Parts of industrial equipment or deliberate traps left by demons, these ceilings will move down to crush anything or anyone that triggers them, which often results in painful death.
Substances:
Water/Radioactive Water: Water is safe as long as it is clean. You can walk in it without fear, and it will conveniently clean your boots from dirt and blood that accumulates there after killing demons. UAC facilities contain water for cooling, irrigation, and drinking purposes. However, bewareradioactive water, which appears normal, but will actually slowly kill you if you do not go out of it quickly, or wear a protective suit.
Boiling/Contaminated Mud: The marine may think some mud cannot do any harm, but it is boiling hot and it causes severe injuries, which may even lead to death. It is a good idea to stay away from suspicious looking mud, or wear a protective suit before entering it.
Cursed Blood: Pools of blood look ghastly, and they conceal great danger for the unwary. Imbued with dark demonic curses, those pools of blood have the property of slowly draining the life of anyone that enters it, until the victim falls dead and is consumed by the vile substance. Oddly, protective suits do block the effect of cursed blood and are an effective contra-measure to its influence.
Toxic Waste: Bright green in color, faintly radioactive, and extremely corrosive, toxic sludge wears away anything within seconds, and eats flesh, leaving only bare bones in its wake. Staying in slime for long inevitably leads to death, and the victims' bodies are often not found as the slime has dissolved everything. Protective suits are the only sure measure against the devastating effect of toxic sludge.
Lava: Lava is created by volcanic activity throughout various areas. It is very hot and causes instant burns and potentially fatal injuries. Even protective suits cannot always stop its effect, so it is advisable for the marine to stay away from lava if possible.
Secret Levels:
(deliberately cryptic hints, so that you can still have the pleasure of finding them on your own)
Military Base: Archives point out that there is an old transport facility at the Phobos base Toxin Refinery. It can take the marine to the Military Base, but in order for him to reach it, he must first gain access to the old, no longer used additional control rooms – very close to the main control room. The marine has to trust his senses and listen carefully for them to reveal themselves.
Fortress of Mystery: The logic of demons is impossible to comprehend for the marine, and he clearly sees no point in stairs leading up to nowhere. But is it really so? What could await beyond the flames?
Warrens: The Warrens are home of the insane, and it is only madness that can take the marine there. He should put aside his reason for a while and let insanity drive him right into the boat that will take him to the Warrens. Yet, be careful, marine – madness is a force that might destroy you, think well before you resort to it.
Fear: The marine might think it is hard to reach the secret UAC facility. From the point of view of a Cyberdemon, however, it is actually quite easy...
Wolfenstein: Hone your senses – look for what appears to be the more illogical, more dangerous way. Take a leap of faith.
Grosse: Trust your memory, marine – it serves you well. If everything around you looks familiar, take the path that you remember from the distant past and it will take you exactly to the same place, just as it did before...
March of the Demons (No Rest for the Living): You must be thorough – explore every dark corner and alcove, even if it seems unimportant. The greatest treasures often hide in the most obscure places...
Bad Dream (Master Levels): You can see the way but it seems to be unreachable? Perhaps a certain kind of demon can help you jump higher.
Pharaoh: Do not be satisfied with something small. Even if you get an unexpected health boost from an unpromising place, do not stop there – keep searching for the greater prize.
Caribbean: It is often true that even if you find a tremendously good and valuable treasure, there might be something you have missed. Go back and check more carefully even if the exit is calling for you...
Cyberden: Do not choose the obvious path. Take a short rest right before you make the last choice of direction, look around, and seek out concealed alternatives...
Go 2 It: You will come to know that the problem is not in finding secret exit, but rather in finding the regular one. Once you enter, there is no turning back. Go to it.
Other Secrets:
Baphomet: There is an ancient saying that Baphomet's face might as well be a mere mask. Those who could look behind it, would see the face of the real creator and master of Hell. Would they have the courage to quickly raise their weapon and strike him down?
Skull Keys: Those artifacts of Hell, which unlock doors, have symbolic meanings. Red skull signifies the blood that demons so much like to spill or consume. Blue skull signifies cold hatred, which drives all minions of Hell into battle against mortals. Yellow skull signifies the eternal fires of Hell that wait to consume the sinful and bring them eternal torment.
Demonic Aggression: Demons are so obsessed with violence and destruction that, when pushed, they would even turn against each other and fight to death. Use this to your advantage!