UAC REPORT FILE: DHVZI9L4
Considered to be the most significant marker of success in the development of Argent-Organic research, the Cyberdemon is the flagship creation of the Lazarus Project. The symbiotic union of a Baalgar demon found during the second Project Lazarus Manned Expedition (MTC 2148/177) and an Argent Accumulator, this beast is capable of withstanding so much punishment that the creature must be kept in permanent suspended animation. Repeated attempts to subdue the beast prove unsuccessful as when exhausted, the Cyberdemon simply replenishes its life force from the Accumulator and attacks again with greater ferocity. Only by removing the Argent implant can the beast be restrained. The Cyberdemon remained in stasis until a suitable method of control can be found.
UAC REPORT FILE: XCZ0UYYZ
The Corrax tablets discovered during the UAC Automated Survey of 2143 mention an ancient battle in the Titan's realm during the third age. An expedition to the plains recovered several relics including the petrified remains of a massive shadow lord believed to be an ancient Baalgar demon. Researchers in the Lazarus Labs began work on piecing the creature back together. At first the project mandate was to construct an educational and inspirational exhibit. However, the focus quickly shifted when an attempt to meld the petrified tissue uncovered that exposure to small doses of plasmatic Argent Energy would reanimate the relic. The potential of creating living, growing tissue from the relic and the lure of an ultimate battle demon was too enticing to pass up. The project team quickly shifted direction and began work melding the ancient remains with high tech weaponry.
UAC REPORT FILE: RRN0R75J
During the Cyberdemon Reanimation Project, the beast was kept alive by controlling the amount of plasmatic Argent Energy it received. This kept the beast in an effectively "brain-dead" state while additional components were cybernetically implanted. A neural pathway was created between the creature's brain and the Argent Accumulator, allowing the creature to administer Argent power to any part of its body as needed. In hindsight, this neural pathway was a mistake as once the pathway was activated the dormant beast immediately administered an Argent surge to the medulla oblongata, which allowed it to restore motor function. Once active, the circulatory system quickly restored and the beast achieved full motor function within a few minutes. It is only through bravery of Follower Jacobson that the beast was contained. Follower Jacobson willingly gave his own life as bait when he lured the giant Cyberdemon into holding pen 6, where it could be contained. Unfortunately, there was no way to retrieve Jacobson once the doors had been bolted, and he was sacrificed.
A report following the incident suggested that this act was not instinct by the Cyberdemon, but rather a suggestion of a greater intelligence governing the will of any creature demon borne - a "mastermind" of sorts. Research on this theory continues.
The physical appearance of the Cyberdemon pays tribute to its original appearance in a number of different ways. It is an incredibly large demon, at least double the size of a Baron of Hell. It has pale, pinkish skin that is covered in a natural armor that covers the majority of its body. It has four small, beady eyes and a large, gaping mouth similar in appearance to a Mancubus or a Prowler. The Cyberdemon has two large, sharp horns, the left horn of which has been broken in half. The Cyberdemon's right arm has a large blade like bone that is located on the wrist which allows the Cyberdemon to utilize its flame wall attack. The Cyberdemon's left arm has been replaced with an orange UAC-engineered rocket launcher. The Cyberdemon's left foot has been repaired with mechanical components. Located on the right of the Cyberdemon's chest is an Argent Accumulator.
The Cyberdemon makes a loud demonic roar towards the Player when alerted. It has a special Rocket Launcher which can launch many smaller missiles at the Player and has the capability to charge up and shoot a massive and powerful laser. It also has an aerial bombardment weapon on its back which can be used to bomb the entire arena. It will also charge in a defensive or offensive action, either moving away from fire or dashing towards the player. When in Hell, it has the ability to throw walls of fire towards the player and raise a straight corridor from it to the Player, where it will proceed to either use the aforementioned flame attack or shoot missiles at the Player.
In order to kill the Cyberdemon, its Argent Cell power core must be removed, and then (while in Hell) it must be weakened and decapitated.
The Cyberdemon has a massive amount of health, so the player must be ready for a long fight. The Cyberdemon has two stages in the fight, where with the first one, in the Lazurus Labs, it will use a random pattern of the attacks mentioned above. After being weakened, the Player can commence a glory kill where they will pull the Cyberdemon's power core out and use it to teleport into Hell. After doing so, the Cyberdemon will seemingly use Hell's energy to revive itself and fully regain health, starting stage two of the fight with a corridor attack. In this stage, the Cyberdemon will fight more aggressively, decreasing time in between attacks, finishing attacks more quickly, and adding the new Hell attacks in with the random pattern. Upon being weakened a second time, the Player can do a final glory kill in which they will stomp off one of the Cyberdemon's horns and decapitate it with it. After defeating Cyberdemon for the first time player will receive achievement "Shoot it Until it dies".
The Cyberdemon's array of attacks can be tricky, but are possible to dodge. When the Cyberdemon begins to shoot missiles at the Player, they must simply keep moving away from the line of fire, same goes with its charge attack. When it starts an aerial bombardment, circles showing each missile's area of effect will show on the ground before they come down. The Player must stay out of these circles in order to avoid damage. Caution must be taken when staying out of the AOEs, however, because the Cyberdemon will continue attacking the player even before the missiles fall, especially in Hell. If the Cyberdemon begins to charge a laser, it will show a targeting line from the rocket launcher following the Player until right before it fires. The targeting line will not simply stay directly on the Player, but rather stay ahead of the direction the player is moving in an attempt to prevent the Player from dodging the attack. Two ways the Player can dodge the attack is by moving the opposite direction right before the laser fires or using Siege Mode on the Gauss Cannon to stun the Cyberdemon, effectively cancelling the attack. In Hell, when the Cyberdemon starts shooting walls of fire, the Player must pay attention to the level of the fire. Walls of fire near the ground can be jumped over, and walls of fire in the air can be crouched under. The same goes when stuck in a corridor, unless the Cyberdemon shoots missiles instead of the walls of fire, which then the Player will need to dodge in between each missile in a quick manner.
If the Player's health is low, a direct shot with the BFG will stun the Cyberdemon and any continuous shots from any other sorts of weapons will cause it to constantly drop health vials which can be picked up to restore the Player's health. Siphon Grenades are also useful. If the Player's ammunition is low, they should switch to another weapon and keep firing, as the Cyberdemon will occasionally drop ammo packs as it is damaged.
- The name of the achievement received after beating the Cyberdemon for the first time is a reference to an April Fool's joke made by Doomworld co-founder Andrew Stine. In this joke, Andrew suggested that in order to kill a Cyberdemon in the original Doom, the player should "Shoot it until it dies".
- In the center of the multiplayer map Helix, there is a chamber with red fluid and a partially finished Cyberdemon in it.
- The Cyberdemon's body shape (especially the legs/"boots") and cybernetic armor bears a striking resemblance to the Praetor Suit. The sleeveless design of its armor also visibly resembles the UAC armor from previous games.
- It is implied that the Cyberdemon is one of the few (if not the only) demons in the game without any fear of the Doom Slayer, due to its grudge against the Doom Slayer for killing it in ages past. Notably, while most demons are either hunted down by the Doom Slayer or summoned in response to the player's attempts to progress, the Cyberdemon appears to actively seek out the Doom Slayer to engage them in battle, even reviving itself after its apparent death and being teleported to Hell proper.