Mancubus

The Mancubus is a cyborg demon found in the DOOM Universe, and has a few distinct subspecies. The Manucubus is rather slow moving due to its size, but what it lacks in speed, it makes up for in the damaging effects of its projectiles.

Biology
The physical features of the Mancubus consist of a large, morbidly obese build, a large bloody mouth with sharp teeth, and twin cybernetic flamethrower appendages, connected to a fuel tank grafted onto its back, with tubes connected to its skin via tubes of the creature's own flesh. The cybernetics on its arms left sickly distinctions where flesh meets machine. Its skin is of a lighter brown complexion, and does not contain any visible body hair. The original, fully organic appearance of the Mancubus is unknown, but it is assumed that the Mancubus had humanoid lower arms and hands. It has two green eyes that lack pupils, and its legs resemble those of elephants, bearing six toes each.

Background
The Mancubi (plural) came from a demonic dimension called Hell. Throughout an unknown period of time, various subspecies of the Mancubus arose. When Union Aerospace Corporation (UAC) scientists were experimenting with teleportation technology on Phobos, they accidentally opened a rift to this dimension. This caused a whole manner of demonic forces, including the Mancubi, to come through the portal onto Mars' moons and the other bases. The demons brought destruction on the UAC bases and killed or possessed many UAC personnel. Not too much later, they made their way to Earth to continue their attack there. A group of Mancubi was tasked with holding an Earth spaceport hostage, as the port held a control unit that would allow Human escape cruisers to get away from Earth and the invasion. It was here that a single hero, a marine, slaughtered the demon hordes, including Mancubi, allowing Humans to escape, and later managed to close the rift between the dimension of Hell and the Earth itself, sealing surviving Mancubi away in Hell. The corpses of Mancubi left on the Martian moons would later be revived by the Mother of All Demons, only for the marine to destroy them again.