Demon (Doom)

"Demon" is the term applied to any species which originated from Hell. During their expeditions into Hell, the Union Aerospace Corporation (UAC) discovered a wide variety of species residing in Hell which were collectively dubbed Demons. While sapience and general intelligence varies between species of Demon, they are shown to be extremely aggressive against all forms of life, including each other on occasion, but ruled by a currently unidentified entity whose voice and testimonies are heard by the being known as the Doom Slayer. (Whether this is the Mastermind later fought by the Doom Slayer, an entirely different being or even the devil himself remains unclear).

History
Little is known about the history of the Demons or even their home-dimension, despite its common reference in various religions, although the Demons have been shown to be capable of accessing other dimensions beyond their own and forcefully integrating them into Hell. During an invasion of an alternative dimension known Argent D'Nur, the Demons were hopelessly outmatched by a group of extremely powerful warriors known as the Night Sentinels. However, they gained the advantage after bargaining with the bereaved leader of the Night Sentinels, offering him the Resurrection of his son in exchange for the Wraiths; the extremely powerful beings which ruled Argent D'Nur. As a result, the Demons claimed Argent D'Nur as an extension of Hell itself, enslaved the Wraiths to produce Argent energy for their own ends, and betrayed the Night Sentinels' leader by resurrecting his son, but in the form of a Demon. At some point in history after the fall of Argent D'Nur, Hell was invaded by an individual known to the Demons as the Doom Slayer; a humanoid being empowered by an angelic entity for the purpose of exterminating all Demons. As legions upon legions of Demons were slain by the Doom Slayer, a colossal Demon known as the Titan challenged him, only to be killed by his hand. Fuelled by unquenchable rage and bloodlust, the Doom Slayer was equipped afterwards with the praetor suit given to him by an unknown individual (The Demon recorded in the Slayer's testimony refused to identify them), enabling to heal his wounds through the absorbing of Argent energy from physical contact with Demons, typically while tearing them apart. Fearing the threat of mass extinction, the Demons lured the Doom Slayer into a trap, collapsing one of their blood temples on top of him and sealing him inside a sarcophagus, marking it with their rune identifying him to warn all Demons of what is trapped inside and that he must never be released. Upon establishing a research facility on the planet Mars, the UAC began to deploy expedition teams to Hell in order to harvest Argent energy, as the Human race had become dependent on it as a major energy source, and Demons to be experimented on for application to military use. However, one of the UAC's researchers, Olivia Pearce, was contacted by the Demons and, upon bargaining with them, converted almost the entirety of the staff of the UAC's Mars facility into a demonic cult, seeking to bring the Demons into their universe and sacrifice Humanity itself to them. Soon after the UAC's Demon specimens are released and the entire population of the facilities staff (apart from Samuel Hayden, CEO of the UAC, who had long since transferred his mind into a robot body to survive a terminal cancer diagnosis) are killed and reanimated by a wave of Argent energy from the UAC Hell portal, the Doom Slayer is released from his confinement. Extracted from Hell by the UAC and dubbed the Doom Marine, he was already present on Mars but inactive until the invasion began. Although the Doom Slayer/Marine was successful in killing the Demon known as the Spider Mastermind, who was apparently responsible for the invasion, along with countless Demons he encountered, future Demon activity is likely to be based on the planet Earth, along with the Doom Slayer's continued one-man war against Hell.

Variants
Possessed - Humans killed and reanimated by a wave of Argent energy, Possessed behave almost identically to Zombies, albeit more hideously deformed, but are easily killed. However, the process of creating Possessed seems to be selective, as UAC soldiers converted into Possessed retain their speed, strength and ability to use firearms.

Unwilling - Possessed which have been transferred to Hell, Unwilling are essentially a more skeletal version of Possessed and behave identically to them. Unwilling are used by the Demons as slave labour and cannon fodder.

Imp - The most common species of Demon, Imps are thin, red and roughly the size and shape of a Human. Although quite weak in terms of durability and damage output, Imps are capable of channelling Argent energy into their hands, producing a ball of fire which they can throw at their enemies. This fireball may also be charged for increased damage. Imps are also capable of scaling walls, allowing them to attack their foe from any vantage point.

Pinky - A large feral Demon dubbed Pinky by the UAC, due to the other species' native to Hell having no name for it, Pinkies are extremely aggressive when faced with prey, recklessly charging at it while using the armour growing around its face as a battering ram to do so.

Hell Knight - A huge brute bred purely for combat, the Hell Knight, while lacking the agility of Imps or any means of ranged combat, is extremely durable and boasts incredible strength, capable of shrugging off most weapons fire, Hell Knights will produce damaging shockwaves through smashing their fists into the ground, stunning their opponent.