Hell

Hell is a cornerstone element of the Doom universe. It is the source of the demonic invasion in the games. It is a dimension from where demons are originated. It has a significant presence in many levels, and is the setting of parts of Doom, Doom II, Final Doom, Doom 64, Doom 3, Resurrection of Evil, Doom (2016) and Doom Eternal.

Overview
Typical features of Hell in these games include copious numbers of mutilated bodies, some apparently still alive, and scatterings of Satanic iconography.

Most of Hell's levels' architecture involves jagged rock walls, fire, inverted crosses, wooden doors, stalagmites, dead trees and lava in place of nukage. Rarely does the player come across natural or technological aspects in the Hell levels, and indeed the structure of the levels themselves do not have any sense of flow or continuity.

In every Doom game, Hell is depicted as having developed biocybernetics or at least have stolen from Earth technology and modified it on their own. Implanting modern and futuristic weapons into the bodies of many of its demons, including powerful demons like the Cyberdemon and the Spiderdemon, which both have mechanical and organic body parts. The Icon of Sin appears to be an enormous, partially mechanical demonic head, though Doom II's endgame text indicates it has a suitably massive body as well.

In addition, in every Doom game, while the laws of physics mostly apply, there is one major violation: rock has the ability to levitate, regardless of mass or size. This is first depicted with Deimos floating above the surface of Hell in Classic Doom, and becomes a regular feature of Hell in Doom 3 and Doom (2016). And it isn't because rock is weightless in Hell, since while non-rock objects and living creatures do obey the laws of gravity, rock can carry them and still levitate, indicating that rock does have weight but also exhibits an antigravity property specific to Hell. (Monsters like Cacodemons are not exceptions, since they levitate on Mars and Earth too, and could be explained by being filled with hot hydrogen gas like zeppelins.)

Inhabitants of Hell
Hell is populated by a wide variety of creatures, from lost souls and zombies to demonic beasts and cybernetic monsters. Not much is known about the exact origins of these creatures. Some of them are likely former humans, while others may have been born (or created) in Hell itself. These creatures are all savage, brutal, and relentless, yet fairly intelligent and able to work together towards a common goal: the conquest of Earth.

In Doom 3, the creatures of Hell are controlled by an entity of great power and malevolence, which refers to Hell's inhabitants as its "children." This entity speaks through Dr. Malcolm Betruger and later manifests itself as the Maledict. It is unknown if this entity is the sole leader of Hell, or just one of the leaders of Hell. In any case, the creatures of Hell obey its every whim. It also appears that the entity has telekinetic powers, as ingame events often show objects and even corpses being levitated and thrown off.

Demonic possession
There are no zombies in the original Doom; the enemies often regarded as such are in fact "Former" Humans possessed by demons from Hell. The Doom Bible states that possession can happen to living but sleeping Humans.

In Doom 3 and Resurrection of Evil, it's demonstrated that both dead and living Humans can be possessed. Most of the civilian and security personnel on the Mars base are possessed and converted into zombies in the first wave of the demonic invasion. These zombies also lack a soul after a given amount of time, as the Artifact cannot absorb a soul from a downed enemy that was a zombie, although it can take souls from any other bodies and in one instance it can take the soul of a man during the game who becomes a zombie in front of the marine and is killed.

For unspecified reasons, some characters — such as the Marine which the player controls — are not taken over. Counsellor Swann, Jack Campbell, Sergeant Kelly, along with a handful of marines and civilians are also amongst those not instantly converted into zombies. Throughout the game, the Marine experiences instances of blurred red vision — usually accompanied by evil laughter or demonic language.

Also, early in the game, when the Marine looks into a mirror he sees a vision of himself starting to become a zombie. These incidents are possibly the result of the demons' unsuccessful attempts to possess him. These events, coupled with the fact that quite a few of the base's military personnel were initially unaffected by the demonic invasion, could suggest that the demons cannot possess those with strong, well-disciplined minds — or at least have difficulty doing it.

A small but often overlooked detail is early in the game when the player finds Dr. Jonathan Ishii you can read his communication that he is trying to send on the screen. It clearly states that if the portal safes fail no biological entity will survive the blast 'radius'. The blast being demonic possession and the radius being in Delta, it is possible that the player and other survivors were on the tip or just outside this radius. This would also explain why more survivors are found early in the game and less the closer to Delta, though this could simply be because the main portal in Delta allowed more demons to come through earlier, and that these demons were able to slaughter the Humans there more efficiently. Later in the game, survivors describe the possession as a shockwave that went through the base. It is possible that the possessions were random and that only a 'burst' or limited amount of lost souls came from the portal. This would also explain why some survived and others did not.

A second process of zombification is also referred to in Doom 3, in which the victim is slowly driven insane by a mysterious ailment. The victim suffers from hallucinations and voices, and becomes increasingly hostile and violent towards those around him. Physical changes occur only at the end stage. This insanity can only be contracted by those who have visited Hell. It should be noted that the Doomguy travels to Hell at one point in the story and suffers no ill effects during or after his trip, although it can be assumed the Soul Cube he obtains may have either protected or cured him from these ill effects.

It can also be implied that demonic possession is not only limited to humans, but also to locations, as the games depict Hell demonically transforming the site that it has invaded. In the original Doom and Doom II, parts of Deimos base and Earth have been seen with walls and floors made out of intestines, spines, and skins. In Doom 3, Sergeant Kelly warns the Marine about an "unidentified growth" taking over parts of the UAC base. The growth depicts spines, skulls, large lumps of moving flesh, and floor tiles levitating from a deep lava pit.

In Doom (2016), Demonic possession occurs via exposure to the Lazarus Wave - a wave of Argent Energy from Hell. Although the Lazarus Wave simply kills most humans without further effects, some victims absorb trace amounts of Argent Energy and are reanimated as the Possessed. When left to their own devices, the Possessed are little more than shambling corpses driven by the most basic instincts. Higher-level demons, however, can command the Possessed through telepathy.

In the classic Doom novels, where Hell is not a part of the story, it is indicated that only dead Humans can be made into zombies, through biotechnology. In the Doom 3 novels, where Hell is part of the story, many of the UAC personnel are possessed just like the game, but some zombies grow claws, jaws and demon-like body parts and others are stronger and faster than the game's zombies.

Access to Hell
In the classic games, Hell is discovered following experiments in teleportation technology, and during gameplay Hell is only accessible by long-distance teleporters or gateways. In the original Doom, teleporters notably have Satanic symbols on them.

Hell in Doom is heavily based on the religious concept that the souls of bad people spend eternal damnation in Hell after death. This is indicated in the Doom II endgame text, "You wonder where bad folks will go when they die now.", and again in The Plutonia Experiment's endgame text, "Hell has gone back to pounding bad dead folks instead of good live ones". Because one cannot physically travel to Hell without the aid of some sort of gateway, Hell's actual location is never revealed, though it is indicated by the Doom FAQ and by the unusual behavior of the environment in Hell in Doom 3 that it is not a part of our universe but rather another dimension entirely. In the classic games, the only way to get physically out from Hell is killing the leader of the demonic invasion such as the Spiderdemon or the Icon of Sin.

In Doom 3, it transpires that teleporter technology was derived from tablets left behind by an ancient Martian race, which went virtually extinct after a full-scale demon invasion on Mars some point in the distant past. Doom 3 also establishes that the demons can create their own portal — known as the Hell Hole — which the Player must destroy in the final level. In the game, it's also possible to exit from Hell with the possession of the Soul Cube, since the Marine only escapes after he recovers the artifact. In Resurrection of Evil, it is revealed that the demonic Artifact acts as a gateway between Hell and our reality, and upon being awakened, enables the demons to invade Mars again.

Differences between games
While the major Doom games all depict Hell, the theme changes slightly between games. The variations between Doom and Doom II are based mainly on levels created by different designers. Doom 3's Hellish atmosphere departs more strongly from the original games.

Doom
In the storyline approaching the beginning of Doom, military experiments are conducted between the gateways at UAC facilities on Phobos and Deimos. Something went wrong, and "soon afterwards, Deimos simply vanished from the sky." In the original Doom, Mars' moon Deimos provides the first link between our universe and Hell.

Deimos' mysterious absence is referred to in Knee-Deep in the Dead's ending text, after the player steps through the gateway at the end of E1M8: Phobos Anomaly: "It...looks like the lost Deimos base." It's later revealed at the end of Episode 2, The Shores of Hell, that the entire moon had somehow been transported to Hell, and is now floating in the air above it, which would no doubt account for the complexes being seemingly warped and taken over by demonic means; more so than the Phobos installations. The gateways, still functioning between Phobos and Deimos, provided the first entryway into Hell.

The original Doom's Episode 3, Inferno, entirely takes place in Hell, where it is depicted as predominately brimstone-covered with a fiery sky, complete with a demonic cathedral and pools of blood. Walls and floors occasionally appear to be made from body parts including human skulls, intestines, spines and skin. In the PlayStation version of the game, Hell's sky is filled with flames, while the Saturn version's stages have a city skyline.

The game's box art, the ending screen for The Shores of Hell, and Inferno's intermission screen depict rocky, barren landscapes. It is unclear if the original Doom's Hell is subterranean in this context, as it could for example be a scorching-hot planet somewhat resembling Venus (although with an atmosphere and temperatures still tolerable by humans).

Thy Flesh Consumed takes place on Earth immediately after the Marine's return from Hell, possibly on a demonic modified UAC base, as evidenced by its endgame text and the episode's resemblance to Inferno's ending sequence. Until the episode was released, the first level to take place on Earth was MAP01: Entryway.

Doom II
Doom II's Hell levels began only after the Marine enters the main gateway on MAP20: Gotcha!. These levels are often closer to subverted human buildings, which implies that some parts of Earth may have been demonically transformed, just like some parts of the Deimos base, with the exception of the last three levels, where it seems to be entirely in Hell. The sky in these levels, where there is any, contributes heavily to the Hellish atmosphere. Notably, unlike in the original Doom, the sky of Doom II's Hell appears to definitely be underground, depicting a deep red cave wall on the horizon beyond craggy brown mountains. According to the storyline, Hell is left in ruins after the death of the Icon of Sin (though this seems more like hyperbole versus an actual description as Hell and its demons continue to exist and engage in further invasions throughout the rest of the series).

Final Doom
Final Doom's portrayal of Hell does not deviate much from previous depictions, and seems to be a combination of the original Doom's cavernous areas and Doom II's building-strewn stages. Hell levels have two different skylines; a "nightmare" red sky in TNT Evilution and crimson sky that looks like stretched, bloody muscle in The Plutonia Experiment (which also somewhat resembles Doom II's skyline). The Hell in TNT has a subterranean feel, and many levels take place in underground caverns. However, some levels have a techbase style, such as MAP22: Habitat, which among other things indicate that the protagonist actually enters Hell at the end of level 24 instead of 20 in TNT.

Doom 64
Doom 64's Hell levels take a dark, cavernous, and frightening approach. There are two separate types of Hell environments: rocky, volcanic areas with a animated burning red sky (some with parallax mountain skylines), some areas with orange skies (with or without parallal mountains),or purple skies (with or without parallax mountains), or similarly-themed mountainous areas with dark blue skies. Some levels may also be complete with thunder and lightning over the mountains. Some levels use the starry sky (seen earlier in planetary "space installation" levels) with Venus and Orion noticeable in the sky. Some levels are filled with atmospheric fog (in different colors), and have no noticeable skylines, while others have light fog, and the skyline can still be seen. Later levels possess a skyline of burning red or green fire against a dead, black sky.

The architecture found in most of the levels resembles castles, cathedrals or temples, replete with Satanic and horrific symbolism, including plentiful pentagrams, inverted crosses, and blasphemous altars. Artwork depicting various demonic/monstrous figures also adorns the walls of the areas. Various human remains are strewn about these levels, including impaled heads, butchered carcasses on meat hooks, and splattered corpses on the ground. Spawned Fear includes outdoors areas resembling  a canyon with grassy areas, and leading to tombs or temples. Some areas have scraggly trees.

Doom Resurrection
In Doom Resurrection the Bravo Team member vists two different locations in hell, Gehenna and Abaddon.

Doom 3
In Doom 3, the Marine ventures into Hell to obtain the Soul Cube. Hell is largely a claustrophobic and cavernous landmass that floats in a void with scattered rock debris alongside other distant rock formations. To an extent, it resembles a demonic take on outer space. Indoors are dark and fiery, although some "outdoor" sections do appear. Mostly, Hell takes place in a large dungeon-like area, finished with huge stone bricks, broken cell gates, glowing Satanic glyphs and pentagrams, and huge oceans of magma. The conventional rules of physics are frequently violated, as for example with chunks of rock floating in the air.

Unlike in the Classic Doom, the atmosphere in this Hell is almost constantly noisy, typically with the crying and moaning of damned souls and extreme sizzling and bubbling of hot magma. People who enter Hell tend to experience a surge of physical energy much like that of an Adrenaline rush: seemingly able to continually exert themselves without tiring. Dubbed as the Hercules Complex by researchers, this effect is noted in the game by the player having an infinite stamina gauge — with flames shooting through it — while in Hell. This Hercules Complex also happens when facing the Cyberdemon in the Hell Hole.

Resurrection of Evil
In Resurrection of Evil, the combat engineer Marine takes a journey to Hell after activating the Phobos Labs portal pad, which leads him to the old Delta Complex from Doom 3. As the Delta Labs and other areas of the Mars Base seem to be dominated by a demonic vortex from the main gateway, the Marine gains access to Hell to return the Artifact in order to stop the invasion.

The environment of Hell has changed since the events of Doom 3, such as the place where the Marine battled against the Maledict, which is eroded and flooded by sizzling magma, and actually resembles the first place which Doom 3's Marine gets teleported into. Unlike the previous version of Hell, which presents itself as a mix of a brimstone tomb-complex and cavernous cave-labyrinth, Hell in Resurrection of Evil seems to be divided into a few more sections, such as the island filled with demons and the whole area seems to have been designed on a larger scale.

Somehow, like in Doom II and Final Doom, when the combat engineer Marine enters Hell, he manages to keep his inventory with all of his weapons upon entering. However his fate is unknown since the human teleportation device no longer exists on Mars, which makes the Marine unable to get back to Mars. This could indicate the Marine died in the last battle, or simply remained there indefinitely.

Doom 2016 and Doom Eternal
In the Doom Reboot series, Hell is described as a realm of pure chaos, unbounded by space, time and dimension that thrives on pain and suffering inflicted on other worlds. The more chaos and desolation Hell inflicts upon the other worlds, the more powerful it becomes.

In spite of this, Hell has a clear hierarchy and a distinct history, with "ages" that are related to whichever demon currently serves as Dark Lord. There have been four distinct Ages of Hell, with the Slayer having been present in Hell during the First Age and his rampage seemingly lasting into the third.

A number of locations in Hell have been visited by the Slayer. The Great Steppe, which adjoins an area known as the Titan's Realm, was the site of a number of battles between the Slayer and other demons, culminating in his defeat of The Titan. He later passed through the skeletal remains of the beast on his way to recover a Crucible.

The Great Steppe connects to the wasteland called the Umbral Plains, a former polar region of Argent D'Nur, via a network of catacombs known collectively as Kadingir Sanctum or the Blood Keep. This area serves as both a fortress, temple and tomb, where demons venerate their own and vilify those who have wronged them. The Doom Slayer himself was entombed in a collapsed temple in this area.

At least two cities are known to exist in Hell: The Necropolis, located within the Great Steppe, and Nekravol. The latter contains the giant Maykr facility known as the Citadel. It is apparently surrounded by an area known as the Blood Swamps, where refuse from its soul extraction operations is discarded.

Another section of Argent D'Nur known as The Well was also dragged into Hell and serves as a processing point where Wraith and demonic energy merge to form Argent Energy.

Less well-described locations include the "blood pits of Angrax" which are home to a demon or type of demon called the Bukavac which strangles its victims, the Penumbral Plains (a location which apparently is home to "heretics") and the glass-shored Lake of Fire.

The Art of Doom companion books name additional locations: a former location called "Babel" of unclear nature which a city called Dis was constructed on the ruins of, and which has "Black Soul Pits" which are overseen by Tyrants. Areas called the Deathlands and the Slough of Torment are stated to be nearby. They also go into more detail about the hierarchy of Hell, stating a group of Archdemons called the Order of the Six serve as subordinates to the Dark Lord, and naming one of them as Erebus, ruler of Dis.

Doom 3 Novels
In the Doom 3 novels, Hell is maintained and the story is largely congruent to that of the game (it is however set a year earlier, and has very different outcome for the characters, and ending. Doom Marine isn't the only survivor, and he loses a leg fighting the Cyberdemon) — making it one of the few spin-offs to maintain this plot dynamic.

The atmosphere of this Hell is very similar to the game, with claustrophobic sections and cavernous planes. But there are more damned souls and possessed human bodies than in the game. The place where the Soul Cube is guarded is changed to an enormous throne which possibly belonged to the Cyberdemon. The Guardian of Hell is also absent, replaced by an enormous horde of demons. John Kane's escape from Hell is also longer and more difficult and dangerous than it is in the game.

Doom without Hell (Doom Novels and Doom Movie)
One of the primary criticisms of the classic Doom novels is that Hell was cut out and the demons instead are genetically engineered aliens. A similar criticism was aimed at the Doom movie, where the monsters were humans mutated by a Martian gene splicing experiment, rather than actual demons, and universally lacked the projectile attacks of their game counterparts.

It is important to note, however, that although the text screens in Doom II refer to an "alien base", the word "alien" is being used in the context of something foreign.

Trivia

 * The Chex Quest analogy to Hell is the Flemoid dimension.