Mancubus/Doom 3

The Mancubus (plural: Mancubi) is one of the few Doom 3 monsters that remain faithful to their original designs, albeit a little. It is greenish-grey in colour, rather than brown like the classic Doom version. Like the original version, the Mancubus is a very large, fat demon with a fireball launcher for each arm, but, unlike the original, it does not fire the two launchers simultaneously, firing each in turn instead. The Mancubus stands about 2 heads taller than a normal human, and its bulk is about 2 to 3 times as wide.

Compared to the classic Doom Mancubus, this one is more elephant or seal-like, or Cthulhu-like, since the Making of Doom 3 book states the latter. Their strange head was explained by the game designers. The central tentacle is a breathing tube, consisting of tiny holes along its sides (which are visible if viewed closely). Both side tentacles were actually supposed to be tusks, making them even more like elephants. Due to a graphical and model design glitch, they were reduced to feeding tools, and are stated to be used like the mouth of an octopus. It is unknown whether they have a beak inside their mouth or not.

The main differences between the Doom 3 Mancubus and the Doom II Mancubus is the skin color, the face, and the feet. In Doom II, the Mancubus had a mouth, leather-imitating colored skin, and elephant-like feet. In Doom 3, the Mancubus has a small "trunk" instead of a mouth, pale skin, and their feet look like fanned out pieces of flesh.

Mancubi are quite rare, and only appear in two levels in Doom 3. It makes it's first appearance in Recycling Sector 2; the Marine enters the area when he begins to feel tremors and a low pitch grunt coming from the monster. Suddenly, the creature crawls out from a waste duct, literally headbutting its way out, then stands up to fight the player. Several are also encountered throughout Hell. They also appear in Resurrection of Evil, and the Lost Mission, although they are mostly confined to Hell.

Combat characteristics
The Doom 3 Mancubus has extremely high offensive capabilities. It primarily attacks by launching a fireball from one of its cannons and then firing the second shot from it's other cannon. It will continue alternating by firing a steady barrage from each cannons.

Unlike the classic Mancubus, the Doom 3 version has a melee attack: the monster can lift up both of its cannons and will smash its target with all it's strength, but not after going through it's long "recharge" time.

Tactical analysis
Contrary to the classic Mancubus, which often posed as a middle-tier monster (similar to the classic Hell Knight), Doom 3's version is a real powerhouse, as it has the highest health out of any non-boss enemies in the game. Their powerful ranged attacks can quickly incinerate a healthy player within a matter of seconds, and their melee attacks is most damaging out of all enemy (second only to the Cyberdemon's stomp). Players are fully justified in using the strongest weaponry in their arsenal to bring one down.

The weapons that are effective against the Mancubus are the Chain Gun, the Rocket Launcher, Plasma Gun, and the BFG. Grenades also work well due to the lumbering speed of these behemoths. Headshots are effective and quite easy to score on a Mancubus, since this creature is a slow-moving and very large target. A Mancubus can be killed with about 4 Rocket Launcher Headshots. If the Soul Cube or Artifact is available, by all means, use it.

Close combat is not recommended against the Mancubus, thanks to the monster's high HP and extremely powerful attacks. However, under extreme situations should the player be forced to fight the Mancubus up close, the Shotgun can work well against these behemoths. You can run and circle around it, then use the Shotgun to hit its back. It will turn to your direction and attack you, however, you can run the opposite way it turns to keep you facing its back (take example: if it turns right, run left) and keep firing the shotgun to finish it off. Areas with columns improve the effectiveness of this tactic.

A Mancubus can be killed with just two of its own fireballs thrown back at it with the Ionized Plasma Levitator.

Trivia

 * If the Mancubus model is examined more closely (e.g. using the noclip cheat or a model viewer), it's possible to see hooks with suckers where the trunk begins, suggesting the trunks are actually feeding tools. Also, when the Mancubus shakes its head, they flap around. This could indicate that the design of the Mancubus was inspired by Cthulhu, like in Quake. The tentacles can also be seen in the beast's introduction FMV.
 * Some of the original Mancubus grunts from Doom II were used in the Doom 3 version.
 * These monsters are usually accompanied by Cherubs in the original and in one level of Resurrection of Evil. This has lead to speculation they are the offspring of Mancubi. This is most likely coincidental, since they look and behave differently.
 * There are only 10 Mancubi in Doom 3 (not counting expansions) : 3 in Recycling Sector (in "their" room) and 7 in Hell (one before the Berserker room, 4 on the hammering pillar room, one on the fiery large room after the Cherubs corridor, one behind the door in this room, and the last one in the corridor next the end of the level).