The '''Mancubus''' is one of the few Doom 3 monsters that remains faithful to their original designs . It is greenish-grey in colour, rather than brown like the [[Mancubus|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 seal-like or [[Wikipedia:Cthulhu|Cthulhu]]-like since the Making of Doom 3 book states the latter. Their strange head was explained by the game designers. The centre 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 [[Wikipedia:Octopus|octopus]]. It is unknown whether they have a beak inside their mouth or not.