Introduced in id Software's Doom II, this hefty hellspawn bears the distinction of being Doom's most overweight opponent. Standing on two short, elephantine legs, the Mancubus is characterized by sagging, leathery brown skin, piercing green eyes, and blood dripping slothfully from its mouth. In place of forearms it has two massive fireball launchers which are powered by a fuel source grafted to its back. A pair of tubes emanate from this beastly backpack and curl over the brute's shoulders, threading themselves through the upper arms before ultimately feeding into the cannons. Upon sighting the player, a Mancubus will let out a sound akin to a low growl which gradually progresses to an angry shout.
Its death animation is also notable for being particularly graphic. The demon lets out a mournful wail as its skull bursts open to expose its brain. Slumping to the ground, its flesh is sloughed from its frame to pool on the ground, exposing its rib cage in the process. As its head hits the floor, the brain comes to rest, framed by two cannons and accompanied by its disembodied eyes.
The Mancubus makes its first appearance in dramatic fashion in MAP07: Dead Simple, where the player is required to fight several in close quarters in order to proceed. This encounter seems intended to showcase its main strength, namely the ability to bombard the player with fireballs in rapid succession. Though certainly dangerous, the Mancubus has several traits which can make for a much more manageable threat. For starters, its portly nature makes it exceedingly slow, allowing the player to fight from range very effectively. As the Doom II manual describes, it is also a "nice wide target." These two facts make it very susceptible to long-range pelting from slow projectile weapons like the Rocket Launcher and the BFG, which it is too sluggish to avoid.
The attack patterns of Mancubi are also highly exploitable. When attacking, they fire a series of six projectiles in three volleys. Once started, they will not stop firing until either the third volley has finished, they have flinched from receiving damage, or they have been killed. Combined with the wide spread of their fireballs, this allows the player to create monster infights very easily just by standing in the general vicinity of another monster. Before beginning an attack, a Mancubus will also telegraph itself with its characteristic bellowing cry, allowing the player time to either find cover or interrupt the attack with a high-powered weapon such as the Super Shotgun.
Though the Doom II Mancubus is certainly the most iconic, there have been a few other versions of id's famous demon doughboy. The most dramatic departure came in Doom 64, where the Mancubus was shown to be taller, thinner, and in possession of a new metal bandoleer. Despite abandoning its corpulent ways, this version was functionally similar, and still carried the signature arm launchers. When id itself returned to the series with Doom 3, it stuck very close to the original design, with the only notable differences being a paler complexion and a new breathing/feeding apparatus which lent its face a Cthulhu-esque appearance.