Hell

Hell in Doom
Hell is an important part of the Doom universe, being the source of all the monsters in the game. In the original and Ultimate Doom, all of Episode 3, Inferno, 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. Doom II's Hell levels are closer to subverted human buildings, with the exception of MAP28: The Spirit World and the last level, Icon of Sin. Other typical features of Hell in these games include copious numbers of mutilated bodies (presumably of the damned) and scatterings of Satanic iconography. In Doom 3, the player ventures into Hell to obtain the Soul Cube (although, in the end, they have no choice). In Doom 3 Hell is a largely dark, claustrophobic, and cavernous plane (although 'outdoor' sections do appear), and is also a place where conventional rules of physics appear meaningless. Hell in Doom 3, unlike in Doom, is almost constantly noisy, typically with the crying and moaning of damned souls.

Hell is depicted in every Doom game as being located in another dimension, and is discovered following experiments in teleportation. In the original Doom teleporters notably have Satanic symbols on them. In Doom 3, it transpires that teleporter technology has been developed based on documents left behind by an ancient Martian race; humanity fails to notice that this race also left warnings not to develop the technology, following a war with Hell.

The final battle with the Cyberdemon in Doom 3 takes place around an enormous portal to Hell located deep under the surface of Mars.

Without Hell
One of the primary criticisms of the Doom novels is that Hell was cut out and the monsters became aliens genetically engineered to scare humans instead.

A similar criticism was aimed at the Doom movie, where the monsters were created by a virus and lacked the projectile attacks of their game counterparts.