Doom Slayer (ドゥームスレイヤー, Doom Slayer), also referred to as the Doom Marine, Doomguy (ドゥームガイ, Doomguy) or just Slayer (スレイヤー, Slayer), is a character from the Doom video game franchise of first-person shooters created by id Software, now owned by Zenimax Media as of 2009, and Microsoft by extension as of 2021.
The Doom Slayer was introduced as the player character in the 1993 video game Doom, in whose story text screens and instruction manual he is simply referred to as "you". Indeed, the original id Software development team deliberately avoided assigning personal identity to the character in an effort to make him an immersive stand-in for the player, leaving him nameless.
In Doom's manual, the character is described as a marine from a futuristic earth. After attacking and critically wounding a commanding officer who ordered his troops to fire on civilians, the marine was transferred to the planet Mars to perform menial guard duty for the Union Aerospace Corporation (UAC) – a megacorporation which uses Mars and its moons, Phobos and Deimos, as sites to perform military-sanctioned testing for interdimensional travel. These tests went lethally awry when the experimental moon gateways opened up from the inside to reveal portals to Hell, from which a glut of demons emerged, mutated the UAC personnel into zombies, and conquered the moons.
In Doom, the marine travels first to Phobos and saves it from the brink of hellish subversion, before making his way to the ruined Deimos base and finally to Hell itself. After destroying the Spider Mastermind who spearheaded the invasion, a portal to Earth is created which allows him to return home – only to find that during his previous mission the demons had conquered Earth, killing much of its human population and his own pet rabbit, Daisy. Doom II: Hell on Earth follows the marine's ensuing campaign to liberate Earth's lone remaining spaceport and enable the surviving humans to escape into space. He then plunges into the heart of his demon-infested home city, locates the portal from which the demons emerged, and returns to Hell to battle the Icon of Sin, the ultimate demon.
Doom 64 sees the marine, now suffering from PTSD as a result of his battles in Hell, forced to return to the fray; after a distant surveillance satellite catches a glimpse of resurrected demonic activity on the ruins of Phobos, the marine is commissioned to return to the moon and finish his work. For a third time, he enters Hell to stop its evil from the inside - but this time, after killing the Mother Demon, he decides to remain in Hell for as long as he lives to make sure that its demonic multitudes will never rise again.
Some time into his personal crusade, the marine is transported into another dimension where he is discovered outside the walls of the city Sentinel Prime by warriors from an order known as the Night Sentinels. When the marine, battered and bloodied, is presented to two of the city's presiding Priests, they note his seeming tenacity and resilience, and command that his mettle be tested in a nearby gladiatorial arena. With his combat prowess proven, the marine is permitted to live, but forced into the front lines of the Night Sentinels' own wars; the Priests, however, are further intrigued by the marine's ramblings of Hell and its denizens, and inform their liege, the angelic Khan Maykr, of a potential new realm to bring their holy word to.
Some time later, the Night Sentinels barely manage to stave off a demonic invasion in their own homeland, and the marine becomes a hero among the Sentinels in the battle. He is knighted a Sentinel himself, and a Maykr chancellor leads him to a mechanical temple which grants him god-like strength and resilience, further increasing his power before sending him to battle a powerful Titan demon. For this and other victories, he finally earns the title "Doom Slayer".
In the aftermath of the invasion, the Khan Maykr establishes parley with Hell and secretly shares her people's advanced technology with the demons, refining the demonic torment of damned souls to achieve an extremely powerful soul-based energy source known as Argent energy. Argent would go on to become the main power source for Hell, the Maykrs, and the Night Sentinels, the latter of whom are kept unaware of its origins; when a battalion of Night Sentinels discover the Argent factories in a mission to hell, they abandon their faith to the Maykrs in disgust, creating a schism that leads to civil war among the Sentinels. The demons take advantage of the situation, persuading a powerful warlord among the Sentinels to lead them to the secret dwelling place of the Wraith-gods who granted the Sentinels their life and magic. The demons slay the Wraiths and use their souls to forge a vast reserve of Argent known as The Well, with whose power they crush the remaining Sentinels and entomb the Doom Slayer inside a demonic sarcophagus.
Back on Earth, the UAC is re-established. It returns to its research on Mars and discovers a fissure on the planet's surface which leaks trace amounts of Argent energy. Reigniting their interdimensional technology, the UAC establishes a gateway to Hell and siphons Argent from The Well for human use, solving a dire energy crisis under the cover story that Argent had simply been a newly-discovered power source native to Mars. Expeditions to Hell allow the UAC to recover a variety of artifacts, among them the sarcophagus in which the Doom Slayer had been sealed, which they extract from Hell and store in the Mars base for further research.
The events of the 2016 reboot, simply titled Doom, begin when the Doom Slayer is released from his sarcophagus to find that the demons had noticed the UAC's probing into their realm and so began tempting a high-ranking UAC researcher named Olivia Pierce into destabilizing the UAC gateway to Hell to allow a much larger invasion. The Doom Slayer pursues Olivia through the Mars base and into Hell, destroying any demons and Argent sources he encounters along the way, eventually killing Olivia after her demonic metamorphosis into a second Spider Mastermind.
In Doom Eternal, the Doom Slayer returns to earth to find it has fallen to a full-scale demonic attack orchestrated by the Khan Maykr and the Hell-corrupted Sentinel Priests, who sought to renew their supply of Argent by harvesting human souls directly. After the Slayer kills the Priests, the Khan Maykr attempts to resurrect the Icon of Sin, its soul now controlled and strengthened by Maykr machinery, in a last-ditch effort to ensure earth's consumption. To stop this ritual, the Doom Slayer returns to Hell and ascends a soul-harvesting facility in the city of Nekravol, in which resides a gateway to the Maykr realm of Urdak. The Slayer invades Urdak and interrupts the binding of the Icon of Sin to Maykr technology, but is unable to stop its resurrection, leaving it alive and uncontrolled on earth. The Slayer kills the Khan Maykr in mortal combat before returning to earth, destroying the Icon of Sin, and saving his homeworld once more, leaving the liberated planet behind to continue his everlasting war against the demons.
The story of Eternal continues in its downloadable content story, The Ancient Gods, which further explores the history of the Maykrs and demons and brings the Slayer through new realms in his goal to unseal and kill the Dark Lord of Hell himself.
As a costume
A DLC costume for Mii Gunner based on the Doom Slayer was announced on October 5, 2021, and was made available for purchase on October 18th, 2021 as part of Round #11. The Mii Costume is based on the Slayer's most recent appearance as seen in Doom Eternal, and is equipped with the Pistol from Doom (2016).
The opening of his reveal trailer features the Slayer walking towards a red Bowser on Port Town Aero Dive, and shooting him with a Charge Blast. The red Bowser represents a Baron of Hell, and the Charge Blast is a stand-in for the BFG9000, which is a large and powerful plasma-based weapon from the Doom franchise. The first-person perspective of this scene references how the franchise codified the first-person shooter genre. The Slayer is then shown fighting a giant Dark Samus in her white costume on the Ω form of Shadow Moses Island. Dark Samus represents the Cyberdemon, a reccurring boss in the Doom games. Next the Slayer is shown fighting Ganondorf on Battlefield's Ω form. The final shot of the trailer shows the Slayer on the Battlefield form of Find Mii lifting Mario in the air, replicating the Nintendo Switch box art of Doom (2016), with Mario standing in for an imp.