Cyberdemon

Cyberdemon is perhaps the most formidable and powerful enemy in classic Doom. It is a tall, muscular, minotaur-like beast with two dark black/grey horns, a cybernetic right leg, a large rocket launcher mounted on its left arm, red wiring on its lower torso, as well as patches of metal and wires on its right arm.

The Doom II manual of the PC version describes the monster in the following way: ''A missile-launching skyscraper with goat legs. 'Nuff said.'' The Doom manual, on the other hand, does not list it, presumably to make its climactic appearance in E2M8 a surprise. The PlayStation, Doom 64, and SNES manual for Doom, however, does make mention of the Cyberdemon: ''Half unfeeling machine, half raging horned devil. This walking nightmare has a rocket launcher for an arm and will definitely reach out and touch you. Make sure you're loaded for bear before you take on this guy.''

Doom RPG
In Doom RPG, the Cyberdemon was created by evil mastermind Kronos by combining human technology with demon flesh.

Wolfenstein RPG
The Cyberdemon was originally known as the Harbinger of Doom. During World War II, he was summoned at Castle Wolfenstein by the Axis army. B.J. Blazkowicz was able to defeat it with the Spear of Destiny, destroying its right leg and left arm. The Harbinger of Doom vowed that it would have a rematch with Blazkowicz's descendents in the future. The prophecy happened in both Doom RPG and Doom II RPG.

Doom II RPG
The Cyberdemon is depicted with two bionic legs in this game, due to a limitation of the game's animation system--each character's legs are required to be symmetrical in design, as the leg sprites (which are separate from the torso and head sprites) are simply mirrored horizontally to create the full set of animation frames for walking. Although artwork was created depicting the Cyberdemon with one "normal" leg and one bionic leg, it was not used in the final game for this reason.

Non-Doom games

 * Main article: Doom references in other games

Trivia

 * In a PC World article, the Cyberdemon was voted as #16 of the top 47 "The Most Diabolical Video-Game Villains of All Time".
 * In Doom (2016) It is said that Oliva Pierce made a "Deal with the devil" and gave Cybernetic enhancements to demons to allow them more power. Which would understand why they are called CyberDemons because they have cybernetic enhancements.
 * The Cyberdemon in Doom II RPG cannot be insta-killed with the Soul Cube.