Cyberdemon

"A missile-launching skyscraper with goat legs. 'Nuff said."

- Doom II instruction manual

Cyberdemons, also known as Tyrants, along with the Spider Mastermind, are very large cybernetic demons, one of which acted as one of the generals in charge of leading the invasion of Mars' moons, Phobos and Deimos.

Biology
The Cyberdemons are extremely powerful, and seem to have been created through the use of horrifying genetic, cybernetic, and biological manipulations to their physical form. The appearance of the Cyberdemons is rather menacing: they are very tall, have a rocket launcher cybernetically attached to their left arm, a robotic right leg, a wired midsection, and a muscular upper body, resembling a minotaur. They bear flat faces with flush nostrils, no lips, and beady eyes set very far apart from each other. The sides of their heads have two large, curving black horns. Cyberdemons have been seen with hooves and somewhat plantigrade feet, and it is unknown if these are two distinct subspecies or the result of evolution/further augmentation. While the original cybernetics of the Cyberdemon are of unknown origin, possibly made by other demons or the Cyberdemons themselves, later cybernetics were more powerful and given by UAC cultists, while still bearing the same overall configuration, with the difference of reinforcing the Cyberdemons' skeletons and organs with more cybernetics. Both the organic and cybernetic components of the Cyberdemons are extremely resilient to damage. The sapience of the Cyberdemon species is unknown, but they are known to be highly intelligent, rule over legions of lesser demons, and display cruelty.

History
The Cyberdemons came from a demonic dimension called Hell. Elder Hell-Gods ordered Cyberdemons, then fully organic beings known as Tyrants, to collect mortal souls who were sinful. The Tyrants ruled over scores of lesser demons and sinners alike, gaining a reputation for being sadistic, lording over the soul pits of Babel. At some point in time, demons gained or stole cybernetic technology, and augmented Tyrants into Cyberdemons. One Cyberdemon led an invasion of Mars, Phobos, and Diemos, commanded by the current Spider Mastermind, ultimately being killed by a lone marine, ending the invasion. More Cyberdemons joined the Icon of Sin in the subsequent invasion of Earth, but were destroyed by the same marine. Years later, corpses of Cyberdemons were revived by the Mother of All Demons, but were destroyed by the marine again. The marine then volunatarily stayed in Hell to put down demonic threats forever, somehow going back in time and across dimensions, becoming the Doom Slayer, an immortal superhuman being who had fought demons for eons.

Later, in what appears to be a different universe, Tyrants were summoned by the Hell Priests, under the direction of the Khan Maykr, to invade Earth. These Tyrants were modified by UAC cultists, becoming even more formidable Cyberdemons, and combated the Doom Slayer throughout Hell, Urdak, and on Earth, coming to the aid of the Icon of Sin. After the death of the Icon of Sin, all remaining Cyberdemons on Earth were gradually killed or banished. Later, when the Doom Slayer sought to destroy the Dark Lord, he fought his way through demon-infested Urdak to the Luminarium, killing more Tyrants along the way. After reviving the Dark Lord, the Slayer fought and killed some more Tyrants on his way to Immora, where Tyrants were present in the Dark Lord's armies and fought against Sentinel forces. A ghostly image of a Tyrant was used to aid the Dark Lord during his final battle against the Doom Slayer. All Tyrants outside of Hell were destroyed when the Dark Lord was killed.

Doom
The Cyberdemon is an extremely powerful enemy in combat, defeating it is very hard without a large amount of ammunition. Melee combat against this beast is suicide due to the amount of hits it would take to destroy the Cyberdemon and also the fast speed of the demon's rocket projectiles. The Cyberdemon can only be hurt by direct hits of a weapon, blast damage does not affect it. The Cyberdemon will fire off a rocket almost as soon as the first one has left, one hit from one of these rockets will cause critical injury. A fight against a Cyberdemon is going to be a long one.