Doom Slayer

Race: Human
Gender: Male
Heigh: 6’8
Weight: 163kg
Eye Colour: Green
Hair Colour: Brown

The demons first gave him the appellation "Doom Slayer" and also refer to him as the Unchained Predator, the Beast, and the Hellwalker. The UAC refers to him as DOOM Marine, or The Slayer.

The Doom Marine was originally a human from Earth who served in the Marines and was dishonorably discharged due to assaulting his commanding officer after refusing to fire upon a crowd of unarmed civilians and was later transferred to the UAC Phobos base as security. The Marine soon found himself trying to prevent the demons of Hell from invading Earth. After having fought demonic hordes through Phobos, Deimos and Hell, he returned home to find Earth overrun by demons and his wife, child, and pet rabbit Daisy, among the billions of people killed, giving him further reason to pursue hunting the demons. He continued fighting the horde on Earth, before taking the fight to Hell once more.

He shows a little more emotion, expressed more through actions rather than words. During his crusade and his interactions with Samuel Hayden (who tries to use and ask the Marine for help) when the latter tries to justify the UAC's actions in Hell as being in mankind's best interests despite the evident risks and aftermath consequences, the Marine responds by angrily dismantling communication equipment at best, and flat-out destroying key UAC equipment at worst despite Hayden's insistence of not doing so. This makes it clear that the Doom Slayer's motivations and priorities start and end with stopping and killing demons and not for the UAC and their economic interests, and very little for anything else. He does, however, show to be sympathetic to a degree as seen when he made a backup copy of VEGA before destroying it, although this could be attributed to the fact the AI opted to sacrifice itself to aid the Doom Slayer in his quest. As such it can be deduced the Marine can show concern for those who either aid him on his demon-slaying mission or otherwise show the necessary resolve to act for the real greater good. Also, despite killing the Khan Maykr, the Slayer understands that she did what she did was for the sake of her race, yet his resolve remains untouched. It's clear that the Slayer cares for humanity in some way, as he is willing to sacrifice not only his relations with the Argenta but also destroy the realm of Urdak in order to stop the demonic invasion of Earth. Despite his war with the demons, he almost never attacks their human allies simply expecting them to get out of his way which they often do. This attitude does not extend to other species or even his allies as he is quick to neutralize them if they would get in his way as seen with his actions directed at The Father and the Seraphim.

The Doom Slayer also appears to be quite intelligent as his original Praetor Suit could be found disassembled in his quarters with numerous parts of it repurposed for his new Praetor Suit, which would make sense, as he previously had the role of an engineer.

According to the Story of the Sentinels codex entries, the Slayer used to speak but later chose not to for reasons unknown aside from uttering "guttural hefts of anger" on his enemies.

The suit is mostly dark green, silver, black, and bronze in color, with slightly lighter legs and helmet. Both the coloration and the overall design of the suit seems to be made to resemble the original Doomguy appearance, though the Praetor Suit covers the Doom Marine's whole body, including his arms. In addition to this the Praetor Suit also appears much more technologically advanced, with a complex visor and internal systems which allows the Doom Marine to travel to Hell and return again unharmed. The suit is described as being made from nearly impenetrable material, and may be responsible for what appears to be the Doom Marine's superhuman abilities. In Doom Eternal, the original Praetor Suit can be found disassembled in his personal quarters, with the interior composed of lots of wiring and large metal frames that hold the exterior armor plating.