DOOM (Eternal) Characters:
Doom Slayer

Game appearances:
DOOM 2016, DOOM Eternal
DLC appearances:
The Ancient Gods Part One + Two
Doom Slayer, DOOM Guy, B.J. Blazkowicz III
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 the him as DOOM Marine, or The Slayer. Before the character had any epithets in the story, he was most commonly called Doomguy in the fan community. This nickname is mentioned in Doom Eternal and used in his dialogue subtitles. He is intended to be the latest iteration and continuation of the classic DOOM Marine who is the protagonist for most of the series. According to Tom Hall and John Romero (who worked on the original Doom), the original iteration of the DOOM Marine was the grandson of Commander Keen and the great-great-grandson of William J. Blazkowicz. Some fan-theories say the Doom Slayer's name could be William Joseph "B.J." Blazkowicz III but according to official interviews the developers clearly stated he has no name. The Doom Slayer's Blazkowicz ancestry may or may not be canonical for the modern iteration. The developers have originally stated that the protagonist has no canon name because he is a representation of the player. When asked directly on Twitter, John Romero replied humorously that his name really is Doom Guy (with a space, in two words - first word for name and second for surname). -- DOOM Fandom (link)
Samuel Hayden

Game appearances:
DOOM 2016, DOOM Eternal
DLC appearances:
The Ancient Gods Part One
Samuel Hayden
History
After coming to Earth for unknown period of time, the Seraphim constructed a human body for himself and fabricated his new name and identity as Samuel Hayden. Under his new identity, Hayden was born to the powerful Hayden family and was known to the public to be a philanthropist and a very prodigious intellectual; having accomplished in several scientific fields, including thermodynamics, electromagnetic theory, and nuclear sciences. He was the founder of the Samuel Hayden Foundation, which promoted the sponsoring of young scientific talent and funding scientific programs in schools and colleges. After Hayden was appointed as General Director of the Global Science Council, the UAC recruited him. Soon after Argent Energy was discovered on Mars, Hayden subsequently took over the leadership of the UAC and began the construction of the Argent Tower. During construction of the Argent Tower, Hayden's body was diagnosed with a stage 4 incurable brain cancer and left with a few months to live. Hayden avoided his death by transferring parts of his brain into a 3-meter tall mechanoid body, allowing him to be virtually immortal. Hayden purposely chose this form for his expeditions into Hell, enabling him to sidestep his Maykr nature that ancient laws prevents him from entering the Dark Realm. After his "rebirth", Hayden was appointed as Project Director of the Argent Facility and under his leadership humanity embraced an Argent-based technological revolution as Argent Energy is integrated into all forms of technology. By the time the Argent Tower finished construction in 2127, Hayden personally dispatched the first Argent package to Earth.
DOOM 2016
Hayden's concerns on Pierce soon unraveled as his former protegee betrayed her mentor and used the Argent Tower to open a portal to Hell, unleashing demons on the Argent Facility and killing all of its personnel. Hayden immediately awakened the Doom Slayer and tried to persuade him to assist him in stopping Pierce. However, he is harshly rebuffed twice at the beginning of the game, though Hayden claims to be willing to accept full responsibility for Hell's invasion. Hayden was able to gain the Slayer's partial cooperation after cutting off his access to the satellite communications array and offering information that he seeks, although in their attempt to stop Pierce, the Slayer later destroyed the Argent energy stations rather than temporarily disabling them as Hayden asked, much to Hayden's irritation.
DOOM Eternal
In 2150, Hayden suddenly resurfaced on Earth before the Allied Nations Council during the time the demonic invasion of Earth had already begun. Hayden recounted the events on Mars to the AN Council before offering to help lead humanity against Hell by providing them his technologies and the Crucible, the last remaining source of Argent Energy in the solar system. The Council appointed Hayden as the Lead Director of the Armored Response Coalition. Under his leadership, Hayden re-purposed the UAC facilities on Earth to produce and supply Argent technology and advanced armaments to the ARC. As the war against Hell grew more dire, Hayden was subsequently given full command over all resistance efforts. With humanity deprived of its Argent-dependent energy grid after the loss of the Well, Hayden invented a method of Argent-Synthesis, a synthetic replication that could recreate the high-yield capability of Argent Energy. Using the Crucible's hidden power, Hayden utilized the artifact as an Argent conductor to restoring the production of Argent energy to Earth. Throughout the war against Hell, Hayden was highly regarded as a mythical figure by human survivors.
The Ancient Gods - Part One
Knowing that the end of the Hell invasion is only temporary, Hayden, the Slayer, and with the aid of the ARC set off in the Mobile Command Carrier with the intent of locating and retrieving the Seraphim, who has been housed in indefinite stasis within the UAC Atlantica Facility, in seeking his help to prevent the demons from using Urdak's realm to reinitiate their invasion. It's there that Hayden starts to speak highly of the Seraphim as "the key to the humans' salvation." Upon reaching the stasis chamber, Samuel requests to be integrated with the Seraphim. This is immediately followed by the Seraphim awakening, revealing Hayden's true identity to be none other than the Seraphim himself. -- DOOM Fandom Full version (link)
Olivia Pierce

Game appearances:
DOOM 2016
DLC appearances:
None
Olivia Pierce
Introduction
Olivia Pierce is a high-ranking researcher of the UAC and the main antagonist of Doom (2016). She was the Head of Biochemical Research at the Argent Facility on Mars and a fanatical researcher of Hell. After coming into contact with Hell's Dark Lord, Pierce made a pact with Hell to aid in their invasion.
History
A former protege of Samuel Hayden, Olivia Pierce was graduated with first class honors in biomechanical and genetic engineering in Strasbourg. After graduating, she was appointed to the Global Science Council and made a fortune by becoming one of the founders of a global research company called NanoStruct Aerospace and Defense Systems. During her two-year tour of duty with the Global Science Council, Pierce once served as a missionary in South America in which she described her experience as a "spiritual but frivolous pilgrimage." Pierce initially rejected Hayden's offer to join UAC as she had no interest in the energy business until her former mentor gave her an artifact, the Helix Stone, from the Argent Fracture. Soon becoming obsessed with the artifact, which slowly corrupted her mind, Pierce made her decision to join the UAC's Lazarus Project as its Head Director after relinquishing her hold on her company. After a few months working in the Argent facility, Pierce suffered from idiopathic scoliosis due to her long-term exposure to Hell, causing her to be bound to a wheelchair. In order to regain her freedom of movement, she agreed to take an experimental augmentation surgery which involved grafting a titanium exoskeleton to her body to replace her damaged spinal function. Despite regaining her ability to walk, moving causes her a tremendous amount of pain due to a side effect of the procedure. However, Pierce refused to take painkillers, believing the medicine would cloud her mind. -- DOOM Fandom (link)
Dark Lord, Davoth

Game appearances:
DOOM Eternal
DLC appearances:
The Ancient Gods Part One + Two
Dark Lord A.K.A. Davoth
Davoth
According to Maykr history, the original Dark Lord was an immortal being once known as Davoth, created by the Father to rule over his first deliberate creation, a realm called Jekkad. Jekkad was a higher plane than the Father's first creation, Urdak, and Davoth was a Primeval, one of the first gods, created to rule over it. However, during the final battle, Davoth reveals that it was he who had created the Father, Urdak, Jekkad, and all living things. According to the Maykr version of history, the people of Jekkad were mortal but made many great wonders, seeking to make their land a paradise: The Father had filled them with ambition without restraint, wishing to see them excel in all things. They were long-lived, but not immortal like the Maykr of Urdak, and it was in this single flaw that the seed of Hell itself was planted. The Father created Davoth with an undying love for his people and a desire to better their lot, and both he and the denizens of his realm came to regard mortality as a curse. Davoth knew that he himself was not mortal, and feared the possibility of his beloved people's extinction, leaving him alone in an empty realm. Guided by Davoth and lacking self-doubt to reign them in, the people of Jekkad turned their intellects towards defeating death itself. The Father saw the future of this endeavor, that Davoth and his people would never cease in their search, regardless of the cost. Foreseeing that this ambition would someday threaten all creation and that Davoth would someday seek to challenge the Father himself, the Father sealed off Jekkad from all other realms. Davoth saw this act as an unforgivable betrayal by his creator, directing his fury at the barriers that encircled his domain as his people continued to fall to mortality. He became the Father's nemesis, the Dark Lord, while his realm would come to be known as "Hell" to the people of Urdak. The once grand and beautiful realm fell into horror and ruin as its denizens set aside all other concerns save for their singular purpose. Davoth continued to test at the boundaries of his prison, with his legions spilling forth into other realms, defeating many forces sent by the Father to stop them. With each victory, the Primeval's power grew greater. Finally, moved to act, the Father entered the despoiled realm and, atop the Pyramid of the Lost, once a temple to the Father, he tore the essence from the Dark Lord's body and cast it down. While Samur Maykr begged the Father to destroy the Life Sphere containing Davoth's essence, he refused, as Davoth was still his own creation: instead, he placed the Sphere in the Temple of Souls. While Davoth was reduced to nothing but a sphere containing his essence, he continued to whisper his influence to the corrupted people of his realm. Ultimately, he would be restored to a physical body by the Doom Slayer through the use of the Maykr device known as the Luminarium, as part of the latter's plan to stop Hell's invasion for good. It is stated by the intern that the only way to truly defeat the Dark Lord (and by extension Hell) was to restore his physical form and then kill him. When resurrected, he appeared in the form of the Slayer. The Slayer tried to execute him there and then, but Davoth informed the Slayer that no blood can be spilled in the Luminarium. Summoning a portal, Davoth told the Doom Slayer that he would be waiting in the city of Immora. The intern would later inform the Doom Slayer that should he destroy Davoth, every demon outside of Hell would be destroyed due to the connection between Davoth and his subjects. -- DOOM Fandom (link)
Personality
Betrayed by his own creations, stripped of most of his power and even name, Davoth was imprisoned for millennia which made him swear vengeance against his servants and everything he created. Malevolent and enraged, he shows no mercy towards others and is fully willing to kill and destroy other worlds. Despite his negative traits, Davoth is also very honorable and is able to show respect to others as is shown during his confrontation with the Doom Slayer, where he fought honestly and revealed his story and the truth about how everything started, as well as the reasons for his actions. After being defeated by his creation, he accepts his fate with dignity and only asks the Slayer if he had anything to say to him, his creator, before he struck him down. -- DOOM Fandom (link)
VEGA

Game appearances:
DOOM 2016, DOOM Eternal
DLC appearances:
The Ancient Gods Part One + Two (The Father)
VEGA
Intro
VEGA is an Artificial Intelligence who helps the Doom Slayer and appears in Doom (2016) and Doom Eternal. In Doom it is first heard after completing the first level and is also the announcer for the Doom Multiplayer Mode. In The Ancient Gods, VEGA is revealed to be The Father.
History
After the Father commanded Samur Maykr to descend into the Earthly realms to guide humanity through their impending discovery of Argent Energy, the Seraph departed his Maykr body and inhabited a cloned human, becoming Samuel Hayden. In order to allow the Father to assist in his duty, Samuel transformed the remaining consciousness of the deity into an Artificial Intelligence made from Maykr technology known as VEGA. This transformation allowed the Father to remain hidden from the Dark Lord, who endlessly seeks to absorb his creator's powers. To further ensure VEGA is hidden from its enemy, the AI was kept ignorant of its true divine nature. As VEGA, it is a polite and helpful AI with a male personality and was made responsible running most if not all of the Mars UAC facility. Shortly after its creation, VEGA's human handlers were stunned by the AI's unprecedented calculating power as it effectively took control of the Mars facility operations upon gathering data from all the UAC subsystems without oversight. VEGA was responsible for proposing a more effective method for processing Argent plasma into Argent Energy, devised better analysis theorems, and even designed new Argent compression schema, allowing for the development of Argent Caches and the Argent Accumulator. VEGA was subjected to the Turing Test by having Computer Science students asking the AI questions, using a volunteering professor to fact check the answers. By the end of the test, nearly 90% of the students were convinced that they were not talking to an AI, but an actual person. What the students did not know is that VEGA also played the role of the professor -- DOOM Fandom (link)
Samur Maykr

Game appearances:
DOOM Eternal
DLC appearances:
The Ancient Gods Part One
Samur Maykr
DOOM Eternal
During the Doom Slayer's journey to Taras Nabad to recover his Crucible, he comes across the Chapel of Purity and the deactivated Divinity Machine; this prompts him to recall Samur (known in the campaign as the "Hooded Figure") helping him into the Divinity Machine. Throughout the events of Doom Eternal there are several explicit clues of Samur being Hayden. Their names are similar, and Samur's lines in the flashback mirror some of Hayden's from Doom (2016). After bringing Hayden to the Fortress of Doom, VEGA states that the architecture of the ship is similar to Hayden's body, and the humans in the ARC Complex remark that Samuel's body is "alien" - this suggests it was possibly based on reverse-engineered Maykr technology. Samuel also seems to have substantial knowledge of Urdak and even the Khan Maykr's weakness, as well as the portal systems in Urdak. When the Slayer enters the Maykr facility with Samuel, the facility refers to him as the Seraphim. Furthermore, when VEGA is placed into an Urdak system, he asks Hayden if he is "the Father," indicating that VEGA may have been created from the Father's essence by Samuel after he stole it from the Maykrs.
The Ancient Gods - Part One
Following the end of the Hell invasion of Earth, the Slayer, Dr. Samuel Hayden, and the Armored Response Coalition embarked on a mission to find Samur, seeking his help to seal Urdak, which have fallen to Hell, and preventing the demons from using the realm's higher dimension to renew their conquests. The Doom Slayer journeyed to the UAC Atlantica Facility where the body of Samur is located. Upon reaching Samur's stasis chamber, Hayden transferred his consciousness into Samur, and revealing that he and Samur are one and the same. Weakened due to his approaching Transfiguration and being unable to set foot in the Dark Realm, Samur tasks the Slayer with braving the trials of the Blood Swamps in Hell in order to retrieve the Father's Life Sphere and returning him into physical form, allowing him to save Urdak from the demons and as well curing Samur's Transfiguration. However, the Slayer proceeded to destroy the sphere right in front of Samur to prevent the Father's interference and further weakening Samur in the process. Without any opposition, the Slayer took the Dark Lord's Life Sphere with the intent of using the Luminarium in the Holt of Urdak to give the Dark Lord physical form in order to destroy him with his subjects. He leaves Samur behind. Upon the Slayer reaching the Luminarium, Samur confronted him, trying to prevent him from resurrecting the Dark Lord. Soon after, Samur is consumed by his Transfiguration and engages in a fierce battle with the Slayer. Ultimately, the Slayer emerges victorious and prepares to kill Samur, only for the Father to rescue Samur and grant the Slayer access to the Luminarium. His whereabouts and condition following this encounter are unknown, but he is presumed to still be alive. -- DOOM Fandom Full version (link)
The Intern

Game appearances:
DOOM Eternal
DLC appearances:
The Ancient Gods Part One + Two
The Intern
Introduction
The Intern is an unnamed employee working at the ARC Complex, and a supporting character in Doom Eternal and The Ancient Gods DLC. He is often depicted as one of the only few humans in the game that doesn't fear the Doom Slayer, as he appears as a fan of the protagonist.
Doom Eternal
Prior to the first Marauder encounter in Mission 6, the Doom Slayer enters the ARC Complex looking for the Crucible, where he encounters The Intern, who eagerly walks up to him and informing him that Samuel Hayden knew he would come eventually for the weapon. After the Slayer gained the Crucible, the Intern explains to him how it is an honor for him to meet him. However, he takes his attention away from where he is going and bumps into the railing by accident. Shortly after, when the Slayer finds the remains of Hayden, the Intern explains how the ARC couldn't revive Hayden as they could not gain access to his main cortex due to it being "alien." He then explains how they were preparing for Hayden's careful extraction with specific orders before the Slayer ripped Hayden's remains right out of the structure.
Quotes
- M...m...my...god...umm...D...D...Dr. Hayden was convinced...um...that you would come here for this...eventually. - The Intern's first meeting with the Doom Slayer. - I, ah, see that your mission objective states that you going to destroy the sphere, not retrieve it? That is not, sir, what Dr. Hayden...the, uh, the Seraphim has requested of us...uh, you. - Listen, whatever we do...I'm in. You want to wake the devil not so you can help the demons...it's so you can kill their leader once he's taken physical form...and that'll destroy all of them, for good...right? -- DOOM Fandom (link)