The legend of the Doom Slayer is a lot more complicated than one would expect, given how light on story the DOOM series is. DOOM Eternal changes that in a big way by providing details and explanation about the world of DOOM we've never gotten before. The codex entries and cutscenes in DOOM Eternal bridge the rebooted series (DOOM 2016 and DOOM Eternal) to the original series and confirm that, yes, the Doomguy, aka Doom Marine, is definitely the same person as the Doom Slayer. There are still some pretty wide gaps to fill in, but we have a more complete picture of the entire story now thanks to DOOM Eternal. Here's how the Doomguy became the Doom Slayer.

DOOM, DOOM II, and DOOM 64

There isn't much you need to know about the plot of the original games in order to understand how the Doomguy became the Doom Slayer. The Doomguy is a marine stationed as a security guard on Mars after assaulting a commanding officer that ordered him to attack civilians. The Union Aerospace Corporation runs a radioactive waste facility on Mars, while simultaneously experimenting with portals to travel between Mars and its moons, Phobos and Deimos. One day, Deimos disappears and demons start pouring out of the portals. The Doomguy fights his way through Phobos, teleports to Deimos which has been teleported to hell. The marine fights his way through hell, killing the Spiderdemon that planned the attack. He is teleported back to earth where he finds a similar demonic invasion is underway. The demons have killed his pet rabbit Daisy, and he is not pleased.

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In DOOM II, the Doomguy fights the forces of Hell on Earth, helping the survivors to escape in a spaceship. He then travels back to hell, kills a giant demon called the Icon of sin, and returns to Earth to help the survivors rebuild society.

The game manual for DOOM 64 explains the incredible toll all of the carnage and trips to hell have taken on the marine. The UAC facility on Mars has been completely quarantined, but a forgotten satellite over the planet reveals that the demon infestation is back and more powerful than ever. The Doomguy must again travel to Mars to eliminate the threat once and for all. Along the way he travels (you guessed it) back to hell where he defeats the Mother Demon. He vows to stay in hell and prevent the demons from ever invading earth again. This is where the Doomguy's story seemingly ends...

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Argent D'Nur And The Night Sentinels

This is when the lore starts to get exceptionally dense. After some time, possibly years, of fighting the demons in hell, the Doomguy is teleported to a planet called Argent D'Nur. The inhabits of Argent D'Nur are called the Argenta and are basically Space Vikings that value strength in combat. The Doomguy arrives in Argent Prime, home of the elite fighting force of the Argenta, the Night Sentinels.

While we don't know how or why the Doomguy was teleported to Argent D'Nur, we know from a flashback cutscene that upon arriving he is crazed and can't stop ranting and raving about demons. He is forced to fight in the coliseum by edict of Night Sentinal law, where his rage and fortitude impress the Argenta.

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Not long after, the forces of hell invade Argent D'Nur. The Night Sentinels are not only caught off-guard but are also ill-equipped to handle the power of Hell. The turn to the guidance of their God Mother, the Kahn Maykr, to help them save their planet from the demons.

Urdak And The Kahn Maykr

The Maykr are a race of celestial beings that come from a world called Urdak. The Argenta worship the Maykr, and in particular, their leader, the Kahn Maykr. The Kahn Maykr is actually the main antagonist of DOOM Eternal and there's a lot about her to dig into.

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Long ago, the Kahn Maykr discovered a prophecy of sorts that suggested someday Urdak and the Maykr would fall, and that the one to defeat them, the "Unholy One," would originate from the Argenta. The Kahn Maykr created the Divinity Machine as a way to screen Argenta for impurities in their soul.

The Maykr were unaware of the Hell and its demon until they invaded, but upon study of a demon they discovered the Essence that gave them power. The Maykr traveled to hell and created factories to harness the Essence from hell and funnel it back to the Argenta. The Argenta used this "Argent Energy" to make the weapons they needed to fight the forces of hell.

Doomguy Becomes The Doom Slayer

The Doomguy, known to the Argenta as "The Outlander," is the only one with knowledge and experience fighting the demons. The King of Argent D'Nur, King Novik, allows the marine to join the Night Sentinels and help them fight the demons.

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The Night Sentinels continued to fight the demons for years, traveling back and forth through the portal to hell. Eventually, the forces of Hell push back in a major show of force by bringing a massive Titan through to attack Taras Nabad, a major city on Argent D'Nur. The Doomguy fights tirelessly, even after nearly all the civilians and Night Sentinels are defeated. The Kahn Maykr's aid, Samur, takes the Doomguy in secret to the Divinity Machine.

In a cutscene, Samur tells the marine that he is offering him a gift that will give him strength and help him on his journey. Upon entering the chamber, the Doomguy is given strength and enhanced abilities. This is how the Doomguy becomes the Doom Slayer. Before the cutscene ends, Samur tells the Slayer, "And now, they will fear you."

Unanswered Questions

There is still a lot we don't know about the events between DOOM 64 and DOOM (2016). Why the Divinity Machine strengthened the marine when it is only meant to purify the Argenta is unknown. We also don't know who Samur really is or what happened to him after upgrading the Slayer.

It's evident from the events of Eternal that the marine is, in fact, the Unholy One that the Kahn Maykr prophesized. While the game ends with all of the Slayer's enemies defeated, a final threat from the Kahn Maykr still lingers: "Your transgressions here threaten all of creation." As she dies, a desperate, unknown cry rings out in the distance. These questions will remain until the next installment, but at least we now know how the Doom Slayer came to be.

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