In all honesty, I am surprised that no one has done a fanfic. I mean, with all the theories that the Doom Slayer is a Blazkowicz, you think at least one person would do this. Well, guess I'll be the first. To do a summary, this takes place between Doom 2016 and Doom Eternal, while also serving as a merger from the former to the latter if that makes any sense.

Sorry, my life has been really shitty right now with this year. I lost my Uncle a few months ago and now a couple of days ago my Abuelo passed away. This year is a real fucking mess if you want my opinion.

Anyway, in addition, the Slayer's Praetor Armor will be the 2016 version because I like that one more. Finally, the Slayer will have the Gauss Cannon, pistol, and weapons from Doom 2016 multiplayer. I hope you all enjoy!

(Baker Shore, Baltic Sea)

"Fand einen anderen (Found another one)." A Nazi soldier said. Raising his rifle, he shot a wounded Allied soldier through the head, instantly killing him.

He and three others were patrolling the shore, with several other squads doing the same. Around them the shore was covered with the wrecks of Allied planes, craters, and bodies of said soldiers. The Allies had attempted to assault Deathshead's Compound, but it had ended in failure against the might of the Third Reich. Now, patrols were sent out to kill survivors or capture prisoners for Deathshead's experiments.

Another soldier sighed. "Das ist so langweilig. Ich bin Lieber woanders (This is so boring. I rather be somewhere else.)." He said as he fiddled with 1946 assault rifle.

The sergeant of the squad gave him a look. "Oh, halt die Klappe privat. Möchten sie lieber abfall entsorgen? (Oh, shut up, private. Would you rather be working waste disposal?)" The sergeant shot back."

A second private chuckled. "Besser nicht. Scheiße riecht besser als dieser mist (Better not. Shit smells better than that crap)." Everyone laughed before their radio suddenly came to life

"Das ist Kader fünf! Wir brauchen Unterstützung! Sofortige Verstärkung anfordern! (This is squad five! We need back-up! Requesting immediate reinforcements!)" The person on the other end shouted frantically. In the background, the sound of gunfire and screaming could be heard clearly.

The squad jolted at the desperation in the man's voice. The sergeant quickly turned on his radio. "Das is trupp zwei. Was ist los? (This is squad two? What's going on?)"

"Wir warden angegriffen! Es schlachtet uns! Es hat bereits drei trupps ausgelöscht! (We're under attack! Its slaughtering us! It already wiped out three squads!)"

"'Es'? Sind es die Verbündeten? ('It'? Is it the Allies)" The sergeant asked. He got no response saved for a final scream before the line went dead.

Before the squad could make any moves, an explosion nearby startled them. Something then came flying towards them before landing right in front of the sergeant's feet. It took a second, but the sergeant came to the horrifying realization that the object was the head of Squad Five's sergeant.

"Da oben! (Up there)" One of the soldiers cried, pointing towards a destroyed transport.

Standing there was a man. Around 6 feet, he wore a green armor of unknown design that covered his entire body. His face was hidden by his helmet's visor. The sergeant took note of the strange red colored design on the left side of the helmet. But his focus shifted towards the object the person was carrying. It was a large device, which had what looked like two prongs on the sides to reveal a barrel in between. The sergeant's eyes widened when the object began to glow blue, but never got a chance to scream.

(With the Doom Slayer)

The Slayer did not even give the dead Nazis a second glance. Instead he put away the gauss cannon and pulled out his combat shotgun as he headed towards the compound.

VEGA spoke up from inside the Praetor Suit. [I am picking up computer activity inside the compound. Gaining access will enable me to learn our current situation]

The Slayer gave a small nod as he recalled what happened. After preventing the demons from invading Mars, the bastard Samuel Hayden sent him away through the tether. The system landed him on the island where he was now, where he quickly figured that he was in the middle of a warzone. The first thing he did was get an understanding of his situation. The Slayer checked his arsenal and was pleased that he was still fully equipped and had his runes too. In addition, the Slayer was able to upload VEGA to his suit, giving him an edge if he could find a computer or something.

However, everything changed when he saw multiple banners and flags with the Nazi symbol on them. He recalled them well as he remembered his ancestor, William Joseph Blazkowicz, fighting against the Third Reich. But what was odd was the fact that the weapons and defenses were far more advanced than what should be possible when the Nazis were around during World War 2. The Slayer was confused. Was he in the past? Or an alternate Earth? He had no way of knowing, but he did have something that could tell him.

Either way it was not the time for that. VEGA put a marker on his visor, indicating where he should go. Without wasting time, the Doom Slayer took off towards a hole in the compound. Before he could get there, however, something intercepted him. It would have crushed him if the Slayer had not moved out of the way. Said thing was, the best way to describe, a giant robotic dog with razor sharp teeth. It even growled like a dog when it realized it missed. Looking towards the Doom Slayer it lunged at him again, its mechanical mouth opened.

The Slayer easily dodged the attack by shifting to the right. Taking out his chainsaw, he tore through the creature's rear leg, cutting off several pieces of metal and wire. Clearly, they were important as the robotic dog nearly lost its footing but managed to save itself from falling. That did not stop the Doom Slayer from taking out his combat shotgun and firing a grenade into its mouth. The projectile exploded seconds later, destroying much of the dog's mouth, with its lower jaw just barely hanging on. It tried one more, feeble attempt to strike at the Slayer with its claws, but the Hell Walker easily dodged the claws again as he rammed his fist into the neck. With a strong heave, he separated the machine's head from the body. With mechanical dog dealt with, the Doom Slayer proceeded inside the compound.

Much of the interior was still intact, allowing the Slayer to storm through without taking too many detours. Fortunately, much of the fighting was focused on the other side of the compound, thus there were not many defenders to interfere with him either. That did not mean he did not run into some guards. This was proven when upon turning a corner he ran into a squad of Nazi Soldiers.

"Eindringling! Töte ihn! (Intruder! Kill him!)" One of the soldiers shouted as he raised his rifle. He didn't even have a chance to scream when the Doom Slayer caved his face in with a single punch. Drawing his combat shotgum, the Slayer blew the head off the second soldier before blasting a hole in the third's chest. The last one managed to fire his weapon, only for the bullets to bounce off the Praetor Suit. Grabbing the Nazi's head, the Slayer bashed it against the wall, sending blood and bits everywhere.

With them dead, the Slayer continued towards the location, VEGA began reporting. [I have intercepted their communications. It seems that an Allied strike force has landed near the beachhead of the compound and are attempting to infiltrate the base.]

Noting the information, the Slayer kept on running. He would encounter Nazi patrols from time to time, only to swiftly terminate them like he did with the first one. Both he and VEGA took note of the advanced armor and weapons they were all carrying. Again, something that did not fit with the current period. Eventually, though, he reached his destination. With a strong kick, the Doom Slayer knocked down the metal doors in front of him. It revealed a large room with several screens that showed various images, including both the outside and inside of the base. There were some Nazi soldiers inside but the Slayer quickly dispatched them. Once the room was clear, the Slayer allowed VEGA to access the databanks.

[Processing data. Date is July 16, 1945. This compound belongs to Oberstgruppenführer Wilhelm "Deathshead" Strasse, head of the Nazi SS Special Projects Division. I have also managed to ID members of the strike force coming here to eliminate Strasse. He is responsible for several advances to the Nazi war machine, enabling them achieve victory of the Allied forces in this timeline. Among them are Royal Air Force Wing Commander Fergus Reid, US Army 101st Airborne Private Probst Wyatt III and finally, OSA Agent and Captain of the US Army Rangers William Joseph Blazkowicz]

That last name made the William Joseph Blazkowicz III AKA Doom Slayer's blood run cold. He still didn't know if the demons were responsible for the technological advancement of the Nazis, but whatever the case, it suddenly made sense why they were in this timeline, in this era. [I have located the survivors of the strike force. They are currently inside the incinerator. Strasse and a group of soldiers are en route towards them. Marking location] VEGA reported.

Pumping his combat shotgun, the Slayer took off. He had no idea what was happening, but it did not matter. For once in his long life, he prayed to the Wraiths he would make it in time.

(With Blazkowicz)

They were in a bad situation. William Joseph Blazkowicz, or BJ as his friends called him, concluded. He, Fergus, Wyatt, and Prendergast were now being held to the floor by these fucking Nazi Super Soldiers. And right in front of him was none other than their target, Deathshead. The sick old bastard's face looked like it went through a grinder, and Blazkowicz had to resist the urge to vomit as the doctor was inspecting all four of them like they were a bunch of animals.

And now he was, "Go on, Captain. Make a choice for me." Deathshead said, indicating to Fergus and Wyatt. What he was asking for was for Blazkowicz to pick one of his friends for Deathshead to use as a fucking experiment! Either the young and inexperienced Wyatt, or the older and foul-mouthed Fergus. If he didn't, then Deathshead would use both of them. It just showed how cruel and twisted the German scientist was. But it turned out that BJ wouldn't have to make a decision.

A force suddenly pounded on the metal door to the room, startling everybody. "What is-" That was all Deathshead could say before the door was knocked off its hinges, destroying the machines behind the German. It was followed by a loud 'bang' with the head of the Super Soldier holding Fergus being blown clean off.

Blazkowicz watched as a tall green armored man came charging through. In his hands appeared to be a smoking double-barrel shotgun. The armored man stopped for a second and though his helmet's visor completely obscured his face, BJ could've sworn he was looking right at him. The armored man then shifted his attention when the two remaining Super Soldiers charged at him, while the third went to protect Deathshead. Fergus and Wyatt took that moment to get out of the way of the battle, with Wyatt helping Prendergast off the floor. Meanwhile, Deathshead turned on the incinerators before fleeing the room with his bodyguard.

Despite all that, even when Fergus was helping him up, Blazkowicz eyes couldn't leave the armored man as he fought the two Super Soldiers. Despite all the shit Deathshead did to enhance them, the soldiers could not keep up with the stranger. Already they had several wounds on their armored bodies, several pieces of said armor having already been blown off. The green man kicked one of the Super Soldiers back while the other one charged, throwing a punch that a normal man would not be able to stop or dodge. The green man, however, was able to grab said arm and easily bent it at an unnatural angle. The Super Soldier's scream was cut short when the green man slammed his fist into its throat, cutting its breathing off.

The third Super Soldier had managed to recover from the kick and proceeded to grab the man from behind, intending to crush him. But it was useless endeavor as the green man slammed the Super Soldier into the wall, crushing some of the incinerator nozzles and blocking the flames. The man repeatedly slammed the Nazi bastard into the wall until the lug released him. Then the green man grabbed the back of the super soldier's head and brought it down right into his waiting knee, caving the thing's face in, hard. He then tossed aside the corpse without a care.

The four Allied soldiers just remained where they were, looking at their savior in awe. They doubted they could have killed those three Super Soldiers and yet this guy took them out easily. "Fuck me, now that's what I call the definition of a bloody badass." Fergus said, breaking the silence.

The green man turned his head to face them, causing the soldiers to subconsciously flinch. Without a word he marched up to them and with his hands, removed their bindings. As Fergus was helping Wyatt and Prendergast to their feet, the armored man held out a hand for Blazkowicz to take. Without hesitation, said soldier took the offered limb and let out a small yelp as he was quickly pulled up. Now standing before this stranger, Blazkowicz could finally see that they were around the same height, give or take a few inches.

"Thanks for the save back there." BJ said to the stranger. For some reason he could tell that this man was an ally. "If you hadn't shown up when you did, I might have been force to made one of the hardest decisions in my life."

If the stranger was going to reply, it was cut off by an explosion, followed by the room shaking. The shockwave caused the Allied soldiers to stumble. "What the bloody fucking hell was that?!" Fergus yelled.

Suddenly the room's loudspeaker came alive. Through it was Deathshead' wheezing voice. "Apologize gentlemen. Normally I would have left you to a much 'controlled' death, but I'm afraid that your new friend has given me little choice but to bring your lives to an…explosive end. I am quite eager, though, to study his new suit once we have recovered your corpses. Abschied (Farewell) my friends." He said before cutting off.

Wyatt looked at the broken nozzles caused by the fighting. A huge amount of steam was leaking out violently and only worsened by the explosions. "Oh man, we need to get out of here or we'll either be burned or buried…or both!"

"The window!" Fergus shouted as he hefted Prendergast, who had a broken foot, over his shoulder. "We need to get the damned bars out of the way!"

Suddenly, the green armored man walked up to said window. Gripping the bars with his hands, he tore them off as if they were made of paper. "…That works." Fergus said.

The armored man moved to the side as the others crawled through the window. The first was Wyatt, then Fergus and finally Blazkowicz. As BJ jumped out, he tried to turn his head to see if their mysterious savior was behind him. He didn't get the chance as the explosion followed a second after. BJ felt something hard hit the back of his head. His conscious fading, the last thing Blazkowciz saw before darkness took him was the green man reaching towards him before he hit the water.

(Hours Later)

The Doom Slayer had moved to slow to stop the piece of metal from striking William's head. Ignoring the three Allied soldiers, the Slayer immediately lunged to grab his ancestor before he hit the water. Moving quickly, he stole a Nazi boat, killing the crew before heading towards a harbor that was near Zakład Psychiatryczny Maławieś, the place that Anya Oliwa worked at.

[His vitals are stable for now] VEGA reported as he did a scan of Blazkowicz who was lying on a makeshift bed. [You have removed as much of the shrapnel as you could. The lack of tools at our disposal will make it difficult to remove the rest. I cannot calculate when he will regain consciousness]

Nodding, the Slayer spotted land up ahead. After VEGA confirmed that the nearest medical facility was the asylum. The sun could be seen behind the town, going down as night started to come. He moved the boat to the edge of the harbor, where no one would see him. Carefully, the Slayer picked up Blazkowicz and headed towards the harbor when suddenly his armor began to beep. Following that were words appearing on his HUD, saying, "Tether system activating."

The Slayer only had a second to put BJ on the ground before he disappeared in a flash of light. Fortunately, said flash, attracted several people passing by. They would then discover Blazkowicz lying on the ground unconscious.

(Elsewhere)

The Slayer stumbled for a moment as he emerged somewhere new. Getting himself oriented, the Hell Walker looked around his new surroundings. The place was a mix of advanced technology and medieval gothic architect. That included several terminals and consoles with his personal mark everywhere, from the controls, banners, and the wall. In front of him was a view of Earth, the air kept in thanks to the energy-window. The Slayer instantly recognized this as his personal Void Fortress, given to him when he was given the rank of General of the Night Sentinels and then made king. He had thought it lost or even destroyed after the fall of Argent D'Nur.

[Doom Slayer, a message has just appeared in your suit. It came online when you uploaded. I wanted to inform you, but the situation at the time called for attention. It is from Doctor Hayden] VEGA said, snapping the Slayer form his musings.

The Hell Walker growled at the mention of the tin corpse. He would rather not listen to whatever that bastard had to say, but given his current situation, he had no choice. Samuel Hayden might even know what the fuck is going on seeing how he was the one who teleported him.

As if understanding the Slayer, VEGA replied. [Very well, playing message] And immediately a window popped up on his HUD and the Slayer was given another visage of Samuel Hayden. The Unchained Predator had to control himself as to not go ballistic at the sight of the tin can.

"Hello, Doom Slayer. If you're watching this then you've succeeded in stopping Hell's invasion of Mars and Olivia Pearce is no more. I'm sorry that I did what I did to you, but it had to be done, though I doubt what I say will matter to you." Samuel said. "You can believe what you want about me, but I meant what I said about being committed in helping you against the legions of Hell. That is why I took the Crucible from you. You and I both know that despite your efforts here on Mars, the corruption of Hell has likely spread throughout the UAC back on Earth and they will invade again. It is only a matter of time."

The Slayer growled again. Although he hated to admit it, Samuel was correct. The demons were good at spreading corruption quickly. And it was a good chance Olivia sent some of her followers back to Earth before unleashing the hell wave on Mars. It was only a matter of time until shit started there. It still did not change it was Samuel's fault that all this started.

"That is why I took the Crucible. Say what you want, but for your world to survive, humanity needs Argent Energy to survive what is to come." Samuel said as if reading the Slayer's mind.

Another fact that Hayden brought up. Earth's technology and weaponry may have advanced since he was last there, but greater civilizations had fallen to Hell, Argent D'Nur was a perfect example of that. And the demons did not always fight fair. However, the Slayer caught onto something Samuel said, referring to Earth as the Slayer's 'homeworld' as if Earth was not the cyborg's…

"No doubt you caught on to the truth." Samuel's message said. "I am most likely heading back to Earth by now with the Crucible. But, even with it and the knowledge I have, you are still needed if mankind is to survive."

The Slayer knew all that. And if Earth's leaders were anything like he knew them to be, they would be doing shit. Politicians were always making problems rather than solving them. It happened on Argent D'Nur too, it was why the civil war started in the first place. That still did not explain why he was even here. Or what happened down below on this Earth.

"I'm sure you have already seen what was happening on the Earth you were just on. Make no mistake, that is the same Earth." Hayden revealed. "Some time after I took you from the Kadingir Sanctum, I began picking up strange energy anomalies…temporal anomalies. Privately, I reconfigured the tether system and was able to discover the source. The demons had somehow managed to go back in time, to World War 2 to be exact, and influenced the Nazi Regime. However, their primary goal is to kill Captain William Joseph Blazkowicz…your ancestor."

The Slayer had already suspected the reason, but this just confirmed it. The demons were not just after consuming the planet, they were after his ancestor. It made perfect sense, eliminate the war hero Blazkowicz before he could conceive a child, and the Doom Slayer would never had existed.

"The demons helped the Nazis win the war by guiding them to a safe keep of the Da'at Yichud. An ancient Jewish society that created inventions far ahead of their time, in truth it was founded by ancient Argenta Colonists of the Bethian Clan of the city of Hebeth, as well as Martian refugees. In the original timeline, the UAC managed to find some of their safehouses and through them, used the technology to advance our space travel, colonizing other worlds, terraforming, and our Argent Energy research on Mars." Samuel explained. "It is clear that the demons have changed tactics in consuming Earth and eliminating you: By killing your ancestor. William Joseph Blazkowicz is a war hero who killed Hitler and ended the worse conflict in human history. His actions are a pivotal point in your upbringing before you even arrived to Argent D'Nur. We cannot allow the demons to complete their goal, no matter what the endgame is. If they succeed, then our timeline will be erased from existence. And to stop them, you will need your fortress, which you are standing now."

The Slayer mentally nodded in agreement. Despite his distrust and suspicions of Hayden's actions and how he even got this information, the Hell Walker knew that the demons had to be stopped. And his fortress would indeed be useful in stopping the demons here and in the original timeline. That still did not answer the question of how it was even here, or how Samuel got a hold of it. The only other being alive who would know about it would be…The Slayer's eyes widened as the truth hit him right in the face.

"I knew that in order to stop them I had to send you to that timeline, and to save your ancestor, stop the demons and the Khan Maykr herself, the fortress was required. After the Deags betrayed you and your comrades, it was thought among many that it was loss. That is how I wanted it as I hid it away should you ever return and have need of it." Samuel, no, the Seraphim, explained. "When I realized what the demons were planning, I sent the fortress to this timeline, and then ensured that the tether system I uploaded to the Praetor Suit would send you there 10 hours after you arrived, enough time to save Captain Blazkowicz."

The Seraphim. Samuel Hayden was the Seraphim, Samur Maykr. Now it all made sense. Though the Slayer wished the idiot would have straight up told him rather than be all secretive about it and shit, at least he got his base back. He headed towards the console as the message continued playing.

"VEGA will be able to plug into the fortress's system. His design was made to be compatible with it." Samuel said.

The Slayer did as he said and uploaded the AI to the station's systems. He waited or a few seconds before the power came online.

[I am fully uploaded to the Fortress. Weapons, shielding, oxygen, tracking, and cloaking systems are all operational. The portal is also usable. The Rift Drive is also working but it has been turned off at the moment] VEGA summarized.

Almost as if following up with VEGA's analysis, Samuel's message said, "At the moment, the fortress is fully powered and can return to the original timeline. However, doing so will use up almost all of the station's power." Samuel explained. "You will need to finish up business there in this timeline first. That is why I took the liberty of stocking your arsenal. You will find them down below in your personal quarters. I trust you will be quite pleased with the collection."

As the message was reaching the end, Samuel said these final words. "I know that you prefer doing things quick and straight forward, but this is not so simple. The demons are clearly using the Nazis as their agents, staying in the shadows until they either finish consuming Earth or kill Captain Blazkowicz. For the time being, you and VEGA must ensure he survives until he is back to fighting strength. And then work with him and whatever living resistance is left to defeat the Nazis. Defeat the Nazis, and you can drive the demons back to hell and then ensure they can never reach this period of time again." He chuckled. "In a way, you should be thanking them. Now you can fight alongside the great war hero William Blazkowicz."

And with that the message ended. Thus, leaving the Doom Slayer alone with VEGA inside his fortress. The Slayer cracked his knuckles. It was still a shock to him, and he was not shocked easily. Then it turned to rage as the realization that the fucking demons wanted to kill his ancestor. The Slayer would show them why that was such a bad idea.

[I have already begun intercepting communications between Nazis forces as well as the Allies too] VEGA said. [I shall keep track of Captain Blazkowciz' condition and inform you of any updates. In the meantime, shall I prepare the portal?]

The Slayer shook his head. It was not yet time to act. Unless Blazkowciz was in danger, the Slayer would take this time to prepare. Check out the armory Samuel had mentioned and upgrade his equipment. And when the time came, the Hell Walker will strike fear into the Nazis just as he did into the demons. In fact, the Slayer couldn't help but grin a little.

He always wanted to kill Nazis.

Done with chapter 1! Hoped you liked this first part. I worked hard on it.

Anyway, I wanted to mention two other things. One is please check out my DoomxWarcraft challenge. And 2, I have another challenge if you're interested.

It's Doom crossover with Arifureta: From Commonplace to World's Strongest. Here is how it works: The Doom Slayer arrives from Mars at the same time that Hajime fell into the Great Orcus Labyrinth and meets him and Yue. The three work together to escape the Labyrinth and the Slayer and VEGA agree to travel with them so they can return to their respective Earths.

The Slayer's relationship with Hajime and his girls would be as a parent figure, or mentor, bonding with many of them, mainly Hajime and Shea. With Myu's case, it would be like an uncle or even grandfather since the Slayer would be fond of her and even let her ride his shoulders. Naturally he would be stronger than anyone. Ehit can also know him because according to the Light Novel, he and his people were fleeing from their world as it was being destroyed by unknown causes, which in this case could be the demons.

Let me know if you're interested and send a private message.