A significantly more powerful, UAC-modified version also appears in the game as the Cyber-Mancubus.
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The Mancubus is a lumbering behemoth demon. A foul odor accompanies its presence, a stench that can be overwhelming if inhaled directly. Mancubi gorge on anything they can find are not adverse to eating rancid flesh. Their diet rots in their digestive system, making their innards highly flammable. These foul creatures are decked in light armor when they reach maturity, but their grotesque frame soon outgrows their armor, exposing their stomach and face.
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Mancubi have taken their disgusting physical condition and turned it into a weapon. As they reach maturity, a chitinous growth begins to form over each hand, creating a hard sheltered "barrel". As the flesh inside decomposes, a noxious effluvium begins to leak from the barrel. The Mancubus can spew this discharge from the barrel over a remarkable distance. The volitale goo ignites under the tremendous pressure, creating a highly effective biomechanical flamethrower.
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Their bizarre physiology can also be their undoing. Their putrid skin covering their soft belly is easily pierced. When exposed, their organs will explode violently, showering a sizeable area with their revolting (and toxic) innards.
The Mancubus is a large, grotesque creature and can be argued as being the most revolting of all the demons. It bears a single green eye similar to a Cacodemon and a large, gaping mouth that constantly hangs open with sharp, rotting teeth. It is covered in armour, possibly made from a chitinous material. The armour covers its chest, shoulders and lower body, leaving its back and enormous, loosely hanging stomach exposed. The stomach displays a large scar that runs down the middle which is kept sealed via a large clamp seen at the bottom. The chest piece bears an orange glowing demonic rune. Covering the Mancubus' arms are two large chitinous growths with two orange glowing barrels that serve as its main armament. The Mancubus also bears piping that leads from its upper back to its arms, possibly for the volatile goo it secretes to traverse towards its makeshift weapons.
The Mancubus is a large, somewhat slow moving monster that can take a large amount of damage and deal just as much. It fires fireballs out of the two cannons mounted on its arms to hit targets at mid to long range and has a flamethrower ability for up close targets as well as a vent attack which will push the player back whilst dealing great damage.
When dealing with a Mancubus, it is wise to strafe around it while firing so as to avoid its cannon fire. As the Mancubus's cannon fire is less accurate at a distance, keeping a gap between the player and the Mancubus is a viable tactic to deal significant damage without being hit. The player should take advantage of its main weakness, the stomach, where upon death will cause the Mancubus to explode, dealing damage to any other demon in the near vicinity. It is unwise to get too close to the Mancubus without a Chainsaw or a Super Shotgun as the Mancubus will use its vent attack to push the player away while also dealing damage. A well placed shot to the stomach with the Gauss Cannon will kill the Mancubus almost instantly. In later levels, especially in Hell, the Mancubus will often appear alongside a Cyber-Mancubus. The player should go for the Mancubus first as it takes less hits to kill and will allow the player to fully focus on the more lethal Cyber-Mancubus.
The Mancubus is also a playable demon in Multiplayer and is the third demon to be unlocked. Despite being labelled as a Mancubus and having similar attacks to one, it uses the model of the Cyber-Mancubus. It roughly maintains the same attacks as it does in the campaign, using its arm cannons to fire its volatile goo at enemy players while also using its vent attack to instantly kill nearby enemies. The Mancubus can take time to master as it requires accuracy and good reflexes to utilise effectively.
As a Mancubus, the player should take care not to let any enemies fire upon you too much when they are in front of you. Despite having 800 health, the Mancubus is very slow moving with a very large weak spot, so the player should take care to eliminate as many enemies as possible with their arm cannons. The player should take great care with their accuracy as misplaced shots could lead to a quick death. The player should also take care to vent as the Mancubus can overheat if they fire their weapons too much. If the player is overwhelmed, they should make use of their vent attack to wipe out most nearby enemies. The vent attack's range also depends on the heat charged. When the heat meter is almost full, the vent attack's range slightly increases.
When fighting against a Mancubus, the player should take advantage of the demon's numerous disadvantages. The Mancubus is slow moving, is a large target and has an easily identifiable weak spot. The player should fire on the Mancubus's stomach as much as possible from a considerable distance. Long range weapons, such as the Heavy Assault Rifle or the Vortex Rifle, are advised as getting too close to the Mancubus can result in the player being killed by its vent attack.
- The Mancubus' bodily explosion can damage anyone within its close proximity when it dies.
- In early gameplay trailers, the Mancubus was originally supposed to fire green fireballs from its arm cannons, and was originally going to glow green instead of orange. It can be assumed that this was passed on to the Cyber-Mancubus, and the Mancubus was changed to fire red fireballs and disperse flames from its arm cannons, more akin to its original appearance in Doom II.
- In the upcoming sequel, Doom Eternal, the Mancubus will return with a different appearance that is closer to its classic counterpart such as having two eyes.