Doom Eternal is full of lore that holds some big twists for the overall Doom franchise--if you know what anyone's actually talking about. Here's a full rundown.
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Note: This post contains spoilers for the stories of, like, every Doom game ever (except Doom 3), and especially the story of Doom Eternal.
Even if you played Doom 2016, you might find yourself a bit lost with Doom Eternal and its much more involved, expansive story. The game starts with a full-scale demonic invasion of Earth, doesn't make clear what's happened since the last game, and for some reason, gives you your own spaceship that's also a castle. Even if you think you're pretty well-versed in Doom lore, you might find yourself lost at the start of id Software's latest--it expects you to know everything from the last Doom game, have a good understanding of lore from two decades of Doom titles, and read a whole bunch of collectible codex entries to fill in the gaps.
While you don't really need to pay attention to Doom Eternal's story to enjoy its intricate combat, there's also a pretty intricate tale being told if you're interested in hearing it. The trouble is, you need to do a lot of the work yourself to follow along, which includes finding a ton of lore collectibles scattered throughout the game. Doing so rewards you with some big revelations about the Doom story, but if you'd rather just get back to ripping and tearing, good news: we've run down the entire tale and all the lore for you right here.
Before we get to the story of the Doom Slayer and his homicidal crusade to kill all demons, we have to set up all the other characters who are a big part of Doom Eternal, but whom you've probably never heard of before. The big villain of Doom Eternal is the Khan Makyr, who represents a race of people from a planet called Urdak--they're essentially angels and the planet is basically techno-heaven. Urdak is so special that it actually exists outside of physical reality, making it almost impossible to get there if the Makyrs don't want you to.
Long ago, the Makyrs were created, or otherwise encountered and were elevated by, an entity known as the Father. It's not super clear who or what the Father was, but its essence stayed in Urdak for a long time, becoming the center of Makyr society. During this time, the Makyrs would undergo a process called the Transfiguration: though they were very long-lived, eventually, Makyrs would start to degrade, and the Transfiguration seems to be some sort of death and rebirth cycle. It sounds like the Makyrs are actually individual people who create a big collective consciousness when they die, so the Transfiguration seems like it's some kind of reincarnation through that process.
Every 10,000 years, the Makyrs choose and create a leader from their collective consciousness: the Khan. That person then leads the Makyrs until the next Khan is chosen, and in that time, the Makyrs are physically incapable of disobeying the Khan. So while there's a built-in term limit for the Khan Makyr through the Transfiguration, the Khan has a lot of power--and they might not want to give that up. That'll be relevant in a minute.
So eventually, something weird happens and the Father just vanishes. Makyr lore suggests the Father's essence might have been stolen by a Makyr called the Seraphim, but the details are sketchy. The point is, the Father is gone, and that messes up Makyr society, and more specifically, the Transfiguration, which now sounds awful for the Makyrs (though we're not exactly sure how). Basically, the Makyrs are scared of the messed-up Transfiguration and the Khan is looking for ways to stop it.
The Story Of The Sentinels
Meanwhile, on a planet called Argent D'Nur, a group of kick-ass space warriors rise and create a society. These people call themselves the Argenta, and they take over their harsh, spooky, and apparently monster-filled world through conquest. They create an army of holy knights called the Night Sentinels, whose job is to protect Argent D'Nur and do justice and whatnot.
The Argenta are such good warriors that they somehow get the attention of the Makyrs, who visit Argent D'Nur and pretty much start getting worshiped as gods. Teaming with the Khan Makyr, the Sentinels start to become a force for conquest to other planets using Makyr technology, which bolsters the magics and tech the Sentinels had already created using their old gods from Argent D'Nur, some strange creatures called Wraiths. The Sentinels start heading to other planets, converting them to also worship the Makyrs, and things are generally good and prosperous for everyone.
It's not really clear if the Makyrs are organic or some kind of big artificially intelligent computer system, but their collective consciousness was able to analyze probabilities to plot out possible futures. In all their future visions, the Makyrs kept seeing the same thing: a Sentinel warrior who would eventually destroy them, who they called the Unholy One. They created something called the Divinity Machine and asked the Sentinels to use it on their warriors to check them for "impurities" that might reveal the Unholy One before he could wreak havoc on Urdak. The Sentinels agreed--it's not super clear what the Divinity Machine is or does, but it was apparently sitting on Argent D'Nur, conveniently available for use in the story later.
Doom Eternal News
Meanwhile again, Doom 1 happens. On Mars, a security guard working in a Mars research facility finds himself in the midst of a demon invasion after scientists researching teleportation technology accidentally open portals to Hell. This Doom Guy goes on a John Wick-style rage mission after his pet rabbit, Daisy, is killed by the demons. He ravages his way through the Mars facilities, driven by little more than the force of his will. Then the demons try to invade Earth in Doom 2, and he fights them there, repelling that invasion. Demons attack another facility on one of the moons of Jupiter in Final Doom; Doom Guy shows up, he kills them all, and he gets even angrier. Eventually, Doom Guy gets so pissed off that he decides to go to Hell itself and kill even more demons in Doom 64.
Doom Guy has a pretty successful campaign in Hell, but after wrecking the Mother of Demons, he decides to hang out in Hell for a while, killing all the hellions he can. But in a new Doom 64 level that's available in Doom Eternal, the Doom Guy gets portaled out of Hell by another boss-level demon.
Doom Guy Arrives On Argent D'Nur
Through the course of Doom Eternal, we get the backstory on the protagonist, the Doom Slayer, that syncs up everything we've covered up to now in one big story. It seems when the big demon kicked the Doom Guy out of Hell, it sent him, perhaps randomly, to Argent D'Nur. There, the Doom Guy was found by the Sentinels and their priests, the Order of the Deag. All the stuff Doom Guy has gone through at this point has driven him pretty much insane, and all he knows is murder, saying stuff like "Rip and tear" and "Guts, huge guts." He comes to be known as the Outlander, and the Sentinels chuck him in their gladiator arena, where Argenta who break the law have a chance to redeem themselves through combat in order to join the army and get a glorious death.
This is the big twist of Doom Eternal: the game reveals that the protagonist from the original Doom games is, in fact, the same person you've been controlling in Doom 2016 and Doom Eternal. He's definitely seen some sh*t at this point, but you've been playing the same Doom Guy this whole time. Eternal fills in the gaps on how it was possible for this regular space marine to turn into the legendary, feared Doom Slayer.
In Doom Eternal, the twist is revealed in a cutscene that finds the Doom Guy showing up on Argent D'Nur, ranting about Hell and demons as he's brought before the two Order of Deag priests you eventually have to hunt down. As it turns out, the Sentinels and the Makyrs had never heard about the Hell dimension before Doom Guy showed up. It seems this might have given the Khan Makyr an idea, or at least piqued her curiosity, to look into Hell's fearsome power.
The Doom Guy excelled in the arena thanks to his murder skills, winning the chance to join the Sentinel army. Not long after, though, demonic portals started to open on Argent D'Nur, with Hell beginning an invasion of the planet. The Sentinels and the Makyrs teamed up to fight them, but found the armies of Hell were unlike any opponent they'd faced before. The demons used some kind of powerful energy source that eclipsed everything the Sentinels and Makyrs had, and they found themselves losing the war.
The Unholy Wars
The Makyrs and Argenta fought the demons for years, and the Doom Guy excelled on the battlefield fighting alongside them. The tide only started to turn late in the war, though, after some of the Sentinels' priests captured some demons and started studying their capabilities. That's when they discovered the Essence, the power source the demons were using. The stuff was intensely powerful, capable of creating weapons, powering cities, healing the sick, and even resurrecting the dead.
As the wars raged on, the Makyrs and the Sentinel priests discovered a way to open portals to Hell and started siphoning Hell's power for their own ends. They called the stuff Argent Energy, and it allowed the Night Sentinels to beat back the demonic hordes. They used Argent energy for their cities, and it made Argent D'Nur more prosperous than ever. The energy was also sent to Urdak, where it allowed the Makyrs to stave off the Transfiguration, living indefinitely. The Khan Makyr became, essentially, all-powerful, because without the Transfiguration, she would never be replaced and could never be defied.
This whole time, the Night Sentinels were a little wary of Argent Energy--it seemed a little too good to be true. They still trusted the Makyrs, but they kept the Argent at arm's length while they kept fighting the demons.
Birth Of The Doom Slayer
Things got bad again when the demons launched a big offensive against the Argenta city Taras Nabad (a place you revisit in Doom Eternal). Hell laid waste to the city and killed just about everyone inside, except the Doom Guy and a group of Sentinels who tried to hold out. Leading the charge was a giant demonic Titan, who was pretty much set to wipe out everything.
Before the end can come, a Makyr called Samur intervenes. He takes Doom Guy to the Divinity Machine, where he zaps him with...something. Argent Energy maybe, it's tough to remember or to follow. Anyway, for some reason, the machine turns the Doom Guy into a superhuman killing machine, and he ceases to be the Doom Guy--instead, he becomes the Doom Slayer we know as the protagonist of Doom 2016 and Doom Eternal. The Doom Slayer rips through the demons and slays the Titan, and for his efforts, gets the unprecedented honor of joining the Sentinel army as an equal to the Argenta.
With the Doom Slayer's help, the Sentinels start winning the war against Hell and things are going pretty well. They start pushing into Hell and fighting the demons on their own turf. And that's when they make a spooky discovery: the Makyrs are, in fact, the bad guys. Shocking.
The Civil War
While the Argenta were fighting their war against the demons, they were enjoying Argent Energy, as were the Makyrs. Toward the end of the war, the Sentinels started finding Argent Energy factories in Hell, created at the Makyrs' behest. Turned out, the Makyrs struck a deal with Hell: in return for an unfettered supply of Argent Energy, the Makyrs would give Hell access to the worlds it had conquered. Oh, and that Argent Energy stuff was actually made out of the tortured souls of the people killed by the demons. The Argenta were enjoying prosperity created from the grisly deaths and torment of their own people.
The Sentinels and their priests, the Order of the Deag, along with the Doom Slayer, were horrified and decided they had to stand against the Makyrs. They tried to open the Argenta to what Argent Energy was, but most people refused to listen, either too blinded by their faith in the Makyrs or too unwilling to give up Argent Energy. That kicked off a civil war between the Sentinels and their king and the Makyr loyalists. And at this point, the Makyrs were fully working with demons as their allies. The Marauders you fight in Doom Eternal are former Night Sentinels who've sided with the Makyrs to become those gross, super-tough-to-kill demon warriors.
After more years of fighting, the Sentinels devised a new plan: Go to Hell and destroy Nekravol, the huge factory that supplies Urdak with its Argent Energy, and cut the Makyrs off. And it might have worked, except for a ton of betrayal.
You know the Hell Priests you have to kill in Doom Eternal? Yeah, those are the Order of the Deag, the Sentinel priests who were supposed to be good guys. They went to work for the Makyrs, but not before using the Sentinel portals to get to Nekravol to scatter their legions across Hell and trap them there.
The Sentinels also had another traitor: Commander Valen. This guy lost his son in the wars, but demons promised to save him from torment in Hell and resurrect him. In return, Valen gave the demons the info they needed to beat the Sentinels with the Deag priests' help. Of course, you can't trust demons, though. Valen's son was resurrected, but not as a human; instead, the hellions turned him into a giant Titan monster called the Icon of Sin (the final boss you fight at the end of Doom Eternal). In his grief and shame, Valen exiled himself to Hell forever, becoming known as "the Betrayer." You meet the Betrayer briefly early on in Doom Eternal, and he's still all upset about everything that happened.
So at this point, the Sentinels are stuck in Hell and getting torn apart by demons. Most or all of them are killed, and the civil war ends with Khan Makyr and her loyalists, the Order of the Deag, victorious. The Makyrs and the Argenta go on from here, invading planets and turning them over to demons to create a constant flow of souls to manufacture Argent Energy. They become more and more twisted and evil because of the power.
Meanwhile, the Doom Slayer doesn't die in Hell. Instead, he apparently spends even more years marauding across the planes of Hell, killing demons and wrecking things for all the evil monsters. It becomes so bad that the demons have whole legends and literature devoted to him in what little culture they have. In Hell, the Doom Slayer is the monster.
Eventually, though, the demons catch the Doom Slayer in a trap. They can't seem to kill him, but they can contain him. The demons manage to separate him from his gear and lock him up in a special magic sarcophagus, where he stays for years. Thus, leading to the opening scene of Doom 2016.
Now we're finally catching up to the latest two games. In Doom 2016, Earth's United Aerospace Corporation, led by founder Dr. Samuel Hayden, finds a way to open portals into Hell. They discover all kinds of cool stuff, including the sarcophagus, a bunch of information about the Sentinels, and Argent Energy. Hayden wants to use Argent to solve Earth's energy crisis and he's okay with a little devil worship on the side if it gets the job done. But some of the UAC personnel take it all a little too seriously: specifically Olivia Pierce, one of the company's researchers.
At some point, Pierce makes a deal with the demons for some serious power in return for helping them invade the UAC facility on Mars where the portals were discovered. It all goes poorly, as Pierce should probably have guessed. The invasion kills just about everyone in the UAC facility, but Hayden manages to wake up the Doom Slayer, who goes back to work.
Now, you might be thinking that it's weird that Doom Guy started out on Earth fighting a demon invasion and then wound up back on Earth fighting another one. That seems to be a function of the Doom universe's various dimensions. Essentially, it seems that Doom is a multiverse, where Hell is a specific dimension, Urdak is another, and it's possible to potentially pass into other universes. Doom Guy started in a universe where Mars was invaded by demons, but by passing into Hell and back out again, he wound up in a new universe, where no demonic invasion of Mars had yet taken place.
Anyway, the Doom Slayer works with Hayden to stop the demons and Pierce, but he also destroys the UAC's capacity for harvesting Argent Energy along the way, much to Hayden's dismay. The Doom Slayer also nabs Hayden's powerful AI, Vega, as he's ripping and tearing, and finds a powerful object called the Crucible, which he eventually uses to stop Hell's invasion of Mars. At the end of that game, Hayden manages to take the Crucible from the Doom Slayer, revealing that it's actually a ludicrously powerful Sentinel sword, as well as an energy source. He then uses portals to send the Doom Slayer to somewhere unknown.
We don't know what happens to the Doom Slayer between Doom 2016 and Doom Eternal, but some time definitely passes. Hayden returns to Earth, where he wants to use the Crucible and Argent Energy to save the planet. But the remaining demonic loyalists in the UAC have other plans, and before long, demons start invading Earth with the UAC's help. Hayden and the world governments create an armed demon-fighting force called the ARC, the Armed Response Coalition, who try to fight back the demons and save the planet. They pretty much spend the entire war losing, however, and with the help of the Hell Priests, demons start to overtake and corrupt Earth.
The war is raging for quite a while until the Doom Slayer finally arrives. He somehow got hold of a Sentinel spaceship called the Fortress of Doom and uses it to return home. The Doom Slayer spends the rest of Doom Eternal stopping the invasion of Earth by killing the Hell Priests, who are pretty dug in on the planet. The Hell Priests are supported by the employees of the UAC, who have turned into Hell cultists to help the invasion.
Through the course of Eternal, the Doom Slayer kills all three priests of the Order of the Deag who betrayed the Sentinels, reunites with Samuel Hayden, reclaims the Crucible and his original Sentinel sword, and eventually makes his way to Urdak to take on the Khan Makyr.
So that's it: All the Doom games are part of one long story, except for Doom 3, which has nothing to do with anything. There are still a lot of loose ends--is Urdak destroyed? What happened to that Samur guy? Was it a great idea to give Hayden control of the Fortress of Doom? What was that other big monster the Khan Maykr had on Urdak, hidden in a giant pool? There's more story for id Software to take on in future Doom titles, and when they happen, we'll be ready to read all the collectibles to explain it to you.