Cyberdemon/Doom 3

"Witness what will be unleashed on Earth!"

- Betruger

The Cyberdemon is the final boss and most powerful demon of Doom 3. It is found at the Primary Excavation Site, where it stands guard over the massive Hell Hole.

This monster is referred to as "Hell's Mightiest Warrior" by the Soul Cube, and further adds that it is the only weapon capable of defeating such entity.

When the Marine enters the Hell Hole, he becomes surprised when he sees the giant monster standing right next to him (almost 5 times taller than the Marine himself). The Cyberdemon then roars at the Marine before proceeding to challenge him.

Physical Appearance
The Cyberdemon in many ways retains its appearance as a minotaur-like giant with a rocket launcher mounted arm like its classic counterpart. However, there are some differences of this new incarnation of the monster. This incarnation has a long tail which extends from the machinery on its back, both legs are mechanical, and the rocket launcher is now located on its right arm instead of the left.

Combat Characteristics
The Cyberdemon primary attacks are similar from it's classic version; it fires a salvo of 3 consecutive rockets from its arm-mounted rocket launcher. Unlike the original version, it now has a melee attack as well: the monster can stomp on the player, doing a whopping 400 damage and killing them instantly even at full armor.

The Cyberdemon in this iteration is also impervious to any of the player's weapons (even a fully-charged BFG shot has no effect on it). Instead, the player has to utilize the most powerful weapon in Doom 3, the Soul Cube, to kill it.

Strategy
The basic strategy for taking down the Cyberdemon is to always be on the move and ensure the towering monster is at a furthest distance possible. Staying at one place for too long will eventually cause the Cyberdemon to close in, making the player an easy target from the Cyberdemon's rockets, or even worse, likely to be trampled to death by it's stomp. Since the player's stamina does not decrease near the Hell Hole, it's best to take advantage of this and constantly sprint to maintain distance from the giant monster.

While the Cyberdemon's rockets are fast, powerful, and travel at a long distance, the player can take advantage of the rocky spires around the Hell Hole to prevent the Cyberdemon from getting a direct shot at the player. However, do not get too close to the ledges as the blasts from the rockets can knock the player into the Hell Hole to their death.

Throughout the battle, Imps and Maggots will be summoned in the arena, either teleporting in or crawling out of the Hell Hole. The player should kill these lesser demons to get the Soul Cube operational. The Rocket Launcher is the best weapon to take them out from a range, as one rocket will instantly neutralize them. However, in worst cases, they can close in on the player if left unattended, so it is best to kill them the moment they are on sight when they spawn in. Alternatively, the Shotgun or the Chainsaw can also work wonders to take them out at close range. But time management is the main priority as the Cyberdemon may close in if it takes more than enough time to kill one individual lesser demon. If situation permits, the BFG can kill multiple Imps and Maggots in the vicinity, allowing the Soul Cube to charge up quicker.

Once the Cube is powered up, have the targeting reticle be focused on the Cyberdemon and make sure to maintain reasonable distance from it. If there's an Imp or a Maggot nearby, the Cube may end up going for it instead of the Cyberdemon, thus wasting the player's shot.

As soon as the Cube has been launched towards the Cyberdemon, quickly move out from its line of sight and start running again. The Soul Cube can briefly stun the Cyberdemon upon contact, which you can use to your advantage to put distance between it and yourself.

Unless in very critical health, the player should have no need to worry too much about picking up any med-kits on the ground, since the Soul Cube will heal the player. If health has to become a huge priority, the player can quickly gather any med-kits nearby to heal quickly. Make sure not to have multiple Imps, Maggots, or the Cyberdemon come after you if they are close. Alternatively, if you have a Cube charged, you can use it to any nearby enemy to instantly regain health.

It takes four charges from the Soul Cube to completely subdue the Cyberdemon. However, to make the fight end quickly, you can have the Soul Cube become fully charged before starting the level. After the boss's intro cutscene, immediately use the Soul Cube, leaving you only the need to charge the Cube three times. After four charges, the Soul Cube will chop off one of the Cyberdemon's legs and then ram onto it's head, finally killing it. The Cube will emerge out from the demon's corpse and then proceeds to enter the Hell Hole, completely sealing the final gateway between Hell and our dimension.

Trivia

 * The Cyberdemon is the only monster from the original games to be a boss.
 * While the Cyberdemon does not make an appearance in the expansion pack Resurrection of Evil, it can be found in the game files of the Doom 3 expansion Resurrection of Evil. When it's spawned (for example by using a cheat code), the Cyberdemon appears to be vulnerable to regular weapon fire, requiring lots of rockets, BFG blasts, or Plasma gun cells to the head in order to fall.
 * Although the Cyberdemon is referred to as "Hell's Mightiest Warrior" by the Soul Cube, the Maledict has nearly twice as much total health and more attacks. This may be because canon-wise, the Cyberdemon may have been an ancient entity that the beings in the Soul Cube may have known for a long time. The Maledict, on the other hand, is a very recent entity (seen at the end of the game), as it is essentially Dr. Malcolm Betruger himself after his transformation.
 * If noclip is used to get close and you punch the Cyberdemon, blood will come out of the robotic parts.
 * The Tyrant's front and back glory kills in Doom Eternal could be a slight nod to the Doom 3 Cyberdemon's death, as both involve having a leg severed and being struck in the head by a supernatural bladed weapon.