The Doomguy, also known as Doom or The Marine, is the protagonist of the Doom series of computer and video games created by id Software. In all the games, he is a space marine working for the Union Aerospace Corporation (UAC), who never speaks (as there is usually no one around to talk to) and is never referred to by name.
In the Doom novels, the main character is referred to as Flynn "Fly" Taggart, which is universally suggested to be the Doomguy from the games. However, Tom Hall's original design draft, also known as The Doom Bible, suggested his name was Buddy Dacote ("Dacote" standing for "Dies at conclusion of this episode", which is indeed the fate of the character, although he continues his adventure in the second episode). In the Doom film adaptation, the main character, John "Reaper" Grimm (played by Karl Urban) is also suggested to be the Doomguy, which comes as a surprise to those expecting the more recognizable Sarge (played by Dwayne "The Rock" Johnson) to take the role.
All of the computer-game renditions of the Doomguy is shown wearing green combat armor. Reaper from the film adaptation wears black combat gear reminiscent of a S.W.A.T. operative.
The Doom Marine's actual face is seen in the game's HUD, where he is shown as having light brown hair, a buzz cut, and blue eyes. The Doom Marine also appears without his helmet in the cover art of Doom II and also in the ending to The Ultimate Doom Episode IV Thy Flesh Consumed. In Thy Flesh Consumed, the marine's face is similar to what is depicted in the HUD, although for some reason his armor and pants are a darker shade of green, perhaps due to wear and tear. His face is never seen in Doom 64.
The Doomguy's personality is never examined in any of the games, although his past suggests that he has a strong sense of right and wrong. In the prologue of Doom, it is told that he assaulted a superior officer when ordered to fire upon civilians. The back of the SNES port box cover describes him as 'one angry marine with a handgun and a bad attitude.' so it can be said that he has a bad attitude. At the start of Doom II, shortly after having arrived on Earth and realizing that a zombie is attacking the people, he instantly blows away the monstrosity with his sidearm. Later, having fought his way to the spaceport and deactivated the force fields to allow Earth's population to escape, he nonetheless volunteers to stay behind and find the source of Hell's incursion. During the events of Final Doom, he promises to slay as many of the Demons as possible after they overran a moon base and slew the entire population (In the TNT: Evilution storyline) and in the Plutonia Experiment, he single-handedly enters the infested UAC complex that contained the Quantum Prototype Accelerators after he learned that an entire Marine platoon with heavy air/ground support are on their way to assault the complex, and because the Marines have never encountered the Minions of Hell, he knew they wouldn't stand a chance. In Doom 64, he is depicted as having nightmares due to his experiences, including the admittedly traumatizing descent into Hell itself. He fights his way through a long-sealed base and descends into Hell once more, alone, and when he defeats the Mother Demon, he decides to remain in Hell to make sure an invasion never happens again. His fate there is unknown.
In Doom, Doom II: Hell on Earth, and Final Doom, he appears to enjoy killing monsters: after he picks up a new weapon, he smiles devilishly; he grits his teeth after firing his weapon for a brief period of time; he clenches his teeth in anger whenever he takes damage and is heard to gasp or scream if killed; and his eyes are constantly and alertly darting left and right. The end game text for Thy Flesh Consumed also reveals that the rabbit killed in a previous cutscene was his pet rabbit Daisy — he is shown holding its severed head with a look of anger and vengeance on his face.
The Doom box picture of Doomguy fighting is the same as the inscriptions found on the Martian tablets in Doom 3, where the Hero is seen fighting the demon horde; however, on the Doom 3 tablet, the location of the demons is reversed and the Hero is portrayed as a muscular figure holding the Soul Cube rather than a rifle.
In Doom 3 the Doom Marine appears similar to his classic Doom incarnation, with the exception that his facial features are not concealed, since he does not wear a helmet (even all other marines in the game wear the same helmet as the original doom guy). He is also less exaggerated, but still muscular. He has black hair and appears to be in his late twenties or early thirties. The 'ab-spot' on the armor is also covered.
There is no background history on the Marine in the remake; apart from the fact that he had just recently arrived on Mars, and is the newest member of the Marine detachment sent on the planet, his past remains a mystery. It is established he is a corporal and was sent to replace one of the marines that had mysteriously disappeared. When Dr. Betruger opens the gateway to Hell, he somehow manages to avoid being transformed into a zombie and ends up fighting through the UAC facility to survive.
This time, Doom's plot is similar to that of the original Half-Life (which itself shared similarities with the original Doom); before the unexpected accident, the player can talk to several people, but most of them do not say much other than the fact they are busy and the UAC base is a frightening place. However, there are several characters, such as Sergeant Kelly, who give the player some briefing regarding his mission, especially after the demons invade the UAC base. Even on these "chatting" occasions, the player character is addressed simply as "marine" and remains silent, likely because most of these discussions are about his orders (this is another similarity with the original Half-Life) or since he is new they do not know his name.
The Doom 3 Marine is portrayed as tough and fearless in the game's cut scenes. He rarely shows fear and only glares at the creatures he comes to witness, including several bizarre and disturbing psychic visions. He only shows a brief burst of fear (stepping back slightly and appearing to mouth the word 'fuck') when he sees the towering Cyberdemon just before the final battle of the game.
In Doom 3: Resurrection of Evil, the main character is a different Marine from the protagonist of Doom 3. This particular Marine is a Combat Engineer, and thus is trained to operate a remote manipulation device known as the Grabber. He has a shaved head, wears blue armor, and appears to be somewhat older than the original Doom marine, based on his heavily weathered facial features.
The game presents very little information on his background, only that he is part of a detachment of Space Marines under the command of Dr. Elizabeth McNeil sent to investigate the Mars UAC facility in the aftermath of the demon invasion. While investigating the Martian ruins he finds and touches the Heart of Hell artifact (simply called The Artifact, also known as the Blood Stone), which releases a wave of energy that disintegrates the rest of his squad and opens another portal to Hell underneath the UAC base.
The Marine in Resurrection of Evil appears to be more anti-hero in outlook, as he seems to enjoy using the Heart of Hell artifact, which ended up killing almost everyone at the base because of him. He also shows brief bursts of anger, especially at the Maledict.
At one time he used a helmet that was the same as the original doom guy.
Grimm's personality can be seen as rather angsty, as he is still dealing with his guilt over his parents' deaths and his concern for his sister, Dr. Samantha Grimm, a researcher at the UAC Mars Facility. However, like his computer-game counterparts, he has no problem killing multiple demons and even his own commanding officer, Sarge, after the latter begins to murder unmutated civilians in order to contain the outbreak and is infected himself in the process.
Near the end of the film, Grimm is fatally wounded and injected with the 24th chromosome by his sister in order to save his life. As she explains, not everyone is made into a monster by the chromosome, and Grimm is instead granted superhuman strength, reflexes, and regenerative abilities. This plot device is apparently the film's way of explaining how, in the games, a single marine can fight an entire army of invading demons and survive otherwise fatal injuries to no ill-effect. These new abilities allow him to stride through the infested base with ease, single-handedly mowing down a small horde of demons; among those killed are many zombies, several imps, a Hell Knight, and a Pinky Demon (all seen by the audience in the game's classic first person perspective). After killing the now-mutating Sarge, Grimm leaves the base with his unconscious sister in hand.