Cybernetics

Cybernetics are a re-occurring theme in the Doom series of games and have appeared in virtually all entries in the series. Most commonly, cybernetics occur in the form of mechanized demons with various weapons grafted onto their bodies and controlled through neural interfaces. This article explores the phenomenon of cybernetics in Doom and serves as a list of all occurrences by sub-series.

Classic Doom
In the Classic Doom games (Doom, Doom II, Final Doom, Doom 64, and their add-ons and expansions), it is implied by the game's instruction manuals, official guides, and other material that the cybernetic demons in the game came to exist via Hell's rapid adoption of human technology stolen from the lost Deimos moon base.

The following classic enemies exhibit cybernetic enhancements:

Doom

 * Cyberdemon - The boss of the second episode, The Shores of Hell, it is the first mechanized demon encountered. Its right leg and left arm are completely replaced with metallic prostheses, and its gored abdomen is filled with red wires or tubes. The left arm prosthesis has a massive rocket launcher in place of a hand. In , it is later suggested that this came about due to the battle between B.J. Blazkowicz and a demon lord known as the Harbinger of Doom, which appears to be the cyberdemon before it received its augmentations. In Doom RPG, which canonically follows after Wolfenstein RPG, it is explained that this cyberdemon was personally converted into its well-known form by Kronos.
 * Spiderdemon - The boss of the third episode, Inferno. The spiderdemon is a creature with a body that resembles a giant brain with a face and two small arms. It achieves locomotion via integration into a large metallic chassis with four legs and a super chaingun.

Doom II

 * Arachnotron - The arachnotrons are essentially simply smaller versions of the spiderdemon, replacing the chaingun with a plasma gun.
 * Mancubus - The mancubus' arms are replaced with large flamethrowers. Two variants occur in the Doom RPG series known as the behemoth and the druj, which are identical save for stats and coloration.
 * Revenant - The revenant possesses metallic upper body armor with two integrated missile launchers, one on each shoulder. Likewise, two variants, known as the ghoul and the fiend, occur in the Doom RPG series.

Doom 64

 * Mother Demon - This mother of all demons is augmented with several metallic struts that run the length of her body, as well as an extension to and reinforcement of her spine. It is unclear if these contribute to her attacks or levitation capabilities in any way, or if those are simply natural skills.

Doom 3
Doom 3, despite its extensive lore offered through PDAs and video disks, offers no in-game justification for the existence of cybernetic demons. However, they occur extensively in the game and in its expansion, Resurrection of Evil, even more so than in the classic series.
 * Bruiser - Occurring in Resurrection of Evil and The Lost Mission, bruisers are more mechanical than organic. Its lower legs are metallic and feature robotic hooves, and both arms are replaced with fireball launchers. Instead of a mouth, the creature has a television screen connected to the lower portion of its face via a fleshy tube - the display changes pictures depending on the monster's actions and mood. A robotic spine can be seen on its back.
 * Commando - The demonic super soldiers created magically by Dr. Betruger from living marines have cybernetic eyes which glow a pale yellow, and -like helmets that appear to be integrated into their skulls.
 * Cyberdemon - referred to as Hell's mightiest warrior, the cyberdemon's body is almost entirely replaced or covered with metal armor, including its massive legs with which it can deliver a fatal stomp. Its upper body has a strange tail-like projection attached, which is likewise entirely cybernetic. It again possesses a rocket launcher for a weapon, integrated into its arm.
 * Demon - The demon has the lower half of its body replaced with a mechanical equivalent, including its two back legs.
 * Lost soul - the lost souls of Doom 3 appear to be disembodied human heads enhanced with a powerful mechanical jaw lined with razor sharp teeth.
 * Mancubus - The mancubus maintains its enhancements from the classic version of the enemy, possessing two mechanical arm cannons in place of its forearms and hands.
 * Revenant - The revenant's upper body is protected by red and white metallic armor which has various tubes running out of it which connect near the enemy's skull. It again possesses two shoulder-mounted missile launchers.
 * Sabaoth - a half-possessed-human, half-tank monstrosity created from the body of Sergeant Kelly after his demonic corruption. He drives himself around on treads and has a large mechanical multi-jointed arm for melee attacks. After attacking and fatally wounding Jack Campbell, he also acquired a BFG 9000, which is mounted on his shoulder.

Doom (2016)
In Doom (2016), the UAC is directly responsible for the development of cybernetic demons, as an entire division was set up on Mars under Dr. Olivia Pierce to undertake this work in the top-secret Lazarus Labs, justified as a weapons development program.
 * Cyberdemon - The petrified remains of an ancient demon shadow lord known as a Balgaar were discovered by the UAC during an expedition to the Titan's Realm. After attempting to weld pieces of the demon back together using Argent energy for display purposes resulted in reanimation of some of the tissue, the Cyberdemon Reanimation Project was started. The demon was augmented with an integrated rocket launcher, multi-missile system, cybernetic leg, and an Argent cache power source. The demon went out of control after its initial activation and could only be subdued using cryogenics.
 * Cyber-mancubus - The cyber-mancubus was created by replacing the normal demon-made armor of the mancubus with UAC-designed protection, integration of an augmented reality visor for behavioral modification and training, and replacement of the mancubus' natural chitinous arm cannons with acid-shooting weapons.
 * Possessed soldier - Though not originally cybernetics-enhanced, the possessed soldiers and their higher tier version, the possessed security, continue to be able to wield their weapons despite the melting of the guns into their arms, seemingly indicating that they are capable of controlling the weapons directly with their nervous systems.
 * Revenant - The revenant program was a major undertaking of the Lazarus Labs, involving the conversion of human test subjects into demonically possessed and mechanically augmented weapons. Subjects were painfully implanted with various systems including a harness with dual rocket launchers and a jetpack, and then subjected to multiple intense Lazarus waves. These resulted in extensive necrosis of tissue and drastic bone growth, and eventually, the conventional death of the subject.
 * Spider Mastermind - Though not created by the UAC like the other demons, the Spider Mastermind possesses technological components adapted and expanded from the full-body exoskeleton of Olivia Pierce. Its mechanical parts include significant armoring on the lower half of its body and portions of its legs and face, a powerful Argent plasma cannon, and two tubes which exit near the face and wrap around to the back of the brain.

Doom Eternal
In Doom Eternal, splinter groups of cultists continue the corrupt work of the UAC.
 * Arachnotron - created from the remains of the Spider Mastermind defeated in the previous game, these smaller spider demons are now mass-produced by an entirely automated factory, its original personnel having been slaughtered by their creations.
 * Carcass - the corpses of human soldiers, reanimated by a mixture of technology and Hell magic.
 * Cyber-mancubus - a heavily armored variant of the mancubus, who does not have the same weak points as its non-enhanced brethren.
 * Doomhunter - the reanimated corpse of an "Agaddon hunter", mounted on a hovertank chassis and grafted with several high-tech weapons, it retains its original purpose of hunting down the foes of Hell such as the player.
 * Dread knight - a cybernetic version of the Hell knight, with energy blades on its arms.
 * Revenant - cultist groups continue the revenant program and have brought some additional refinements. One innovation is the creation of revenant drones that can be remotely-controlled through a neural link.
 * Tyrant - these lords of Hell have received the same enhancement as the balgaar-based cyberdemon prototype from the previous game. Although they are not referred to as cyberdemons, their design is very close to the original cyberdemon from Classic Doom.
 * Whiplash - these sneaky demons can crawl at high speed on their mechanized serpentine tail to attack with Argent energy whips.
 * Maykr drone - cybernetic angelic beings built by the Makyrs, known to be enemies in late game. They have retained only organic brains, the rest of their body is replaced with cybernetics, they can shoot lasers.
 * Cyborg zombies - mechanized versions of standard Earth zombies, armed with combination flamethrower/blaster mounted in place of their right forearm.