Somewhere in the orbit of the earth, a small flickering red light can be seen. The red light flickers faster and faster, slowly growing larger. Suddenly, with a brilliant flash of bright red, a massive floating castle-like space station slowly glides into this new universe with an ear-splitting roar.

Inside the station, all power is off. Only a slight hum can be heard, slowly increasing in intensity. After a few moments, a single monitor flicks on, and a speaker can be heard. “Awaken, slayer.”, droned the cyborg Samuel Hayden in a monotone voice. “We appear to have been pulled into a different reality. I am attempting to power the Fortress.” After a few seconds of humming, the Fortress of Doom’s power and lights flickered on. The slayer stood up, having fallen to the ground due to tremendous shaking, and looked around. “Slayer, I only have 20% power to work with.” said Hayden, “ I will need more power to get us out of this reality.”

The slayer walked over to the nearest monitor, which displayed a map of the earth. He simply pointed towards it. “Understood. I am scanning earth now, slayer. 30%. 64% 100% complete.” reported Hayden. “It appears that this alternate earth is also facing an infestation. However, I detect no argent energy whatsoever. This earth appears to be a past one.”

The Slayer simply pointed to the map of the earth again. “Understood, slayer.”, Hayden responded. “Connecting to local news feeds right now.” A secondary monitor in the control room flickered on, displaying a channel called “FOX news”. The stereotypical news anchor said “Good evening, folks at home. In a surprising turn of events, the extraterrestrial creatures who we call “ponies”, have declared war on all of humanity. Here’s a clip of the statement from their leader, who is referred to as “Princess Celestia”. Run the clip, Tim! “

“Citizens of Earth. Humans. I, Princess Celestia, leader of the nation of Equestria, declare war on all evil. Humans are flawed. Inherently evil. I vow to change this, spreading the ways of harmony by force. However, you have an opportunity. Surrender now, and lives will be saved. Those we cannot convert will have to be killed.”

“You, All of humanity, have 12 hours to respond.”

After a few moments of silence, Hayden said “Slayer, this was 14 days ago. Through the use of forced genetic modification through gases of unknown origin, the ponies can convert any human to a pony. These transformed beings forget their past lives and are instantly brainwashed by “Celestia''. Earth is 60% consumed.”

The Slayer silently pondered as Hayden continued to speak. “I sense artifacts of great power belonging to those “ponies.” I require possession of them for our return to our native reality, Slayer.”

The Slayer silently processed this. He simply turned, walking towards the main portal frame and pressing the button to activate it. “Before I prepare the portal, you will need weapons, slayer,” said Hayden. “I only have enough power to manufacture one. What is your choice?”

The Slayer walked over to the fabrication machine, selecting an item from the small selection screen. “The combat shotgun is fabricated, Slayer. Enter the portal when you wish.”
The Slayer cocked his shotgun, nodded slightly, and entered the portal.

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“SENDING THE BOMBER PEGASI”, Shouted a pegasus dressed in armor. “Keep squadrons 3 and 4 as reserves. We don’t know if those humans will survive our attack.” calmly responded Air Ace, a grey pegasus. “We need to take out this rebel camp so we can advance.”
As ponies scurried around the temporary base full of chariots and tents, he contemplated what the next move would be. Humans had already proven very resilient, however, when attacked with gas, were completely unprepared. Many smaller countries had surrendered immediately, and human weapons were weak against shields. Princess Celestia was using a powerful artifact of unknown origin to power her massive shield that slowly expanded, preventing all human “Bomber Planes” and “Missiles” from entering.

The ponies had the full advantage, but recently, they had run into fierce rebel resistances as enthusiastic as they were unorganized. They struck out in guerilla attacks, in the dead of night, and simply wanted to kill as many of the ponies as possible. Currently, they are raiding a rebel base located in “Mexico City”, an urban jungle with many decrepit abandoned buildings.
In a massive “Zoo”, these humans made a compound with shacks, armories, battlements, and pits to stop ground charges.

They even had a powerful weapon, called a “tank” with a massive weapon similar to Griffon cannons. Pegasi dropping ponification potions and gas canisters were currently raiding the base. Suddenly, an assistant ran into the command tent, yelling “Captain help! We have an uhh… situation. Quick, look over here.” He used his horn to pull up a magical screen, scrying upon the friendly troops. These were special-ops ponies, making their way through the inner parts of the compound. They were making their way through a well-lit hallway, with unicorns in the back making a magical shield, and earth ponies upfront with melee weapons and metal shields.

"Advance slowly, lads.", said the leader of the group, a grizzled veteran who had led numerous missions. "These human bastards are sneaky."

Suddenly, a massive human with insanely muscular arms wearing full protective armor busted through a door in front of them. He dashed forward, walking through the shields placed by the unicorns, slamming his fist directly into the first earth pony shield, shattering it completely with only his fist. He activated a wrist-mounted blade, brutally slamming it into the head of his first opponent, resulting in a massive spray of blood and gore.

“QUICK RETURN FIRE”, shouted the squad commander, but it was too late to react.

By the time the unicorns prepared to launch magic at this hulking beast of an opponent, he was inside the shield, pulling out his weapon, and letting it rip. A stream of rapid-fire buckshot left the barrel, turning the small frames of the unicorn spellcasters into red mush riddled with bullet holes. After he ran out of ammunition, he removed what appeared to be a vibrating spiked blade from his back, pulling a ripcord, and sawing the last pony left standing clean in two.

The screen cut out, and after a few moments of silence, “We need some special forces to deal with this bastard. ALRIGHT, EVERYPONY, I WANT VISUALS ON THIS MADMAN, STAT. WE NEED TO PREVENT HIM FROM GETTING HERE.” Ordered Air Ace, while the rest of the tent resumed its activity. “What was that?” asked his second-in-command, Blade Dancer, a female earth pony. “I don’t know”, said Ace, “But I don’t want to be the one who finds out.”

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The Slayer appeared in this new world. Right away, he sprang into action. He immediately started to walk through the halls, searching for his target.

“I will mark the targets on your HUD, Slayer.”, helpfully said Hayden. “You will need to eliminate the targets and claim their necklaces, which consist of extremely powerful ‘harmonic’ energy.”.

The Slayer nodded, and busted through the door in front of him, rounding the corner into a hallway, and spotted some opponents. He sprinted over, slamming his fist into their shield, disabling it, and activated his fully automatic shotgun attachment, shredding his opponents. He swapped over to his chainsaw and sawed the remaining opponent clean in half.

After dealing with his first threat quite quickly and efficiently, he continued through the halls of the makeshift compound, smashing ponies as he passed them.

“Slayer, I suggest you make a stop at the armory of the local humans. My initial scans indicate many weapons for your use.”

The Slayer paused after hearing this, then turned to the left towards the armory, and started marching. After a few minutes, he walked up to a locked door, which he smashed in with his fist.

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Hugo was having one hell of a day.

Ponies had invaded a few days ago, ruining his life completely. He had quickly joined up with a military force for safety, and after he messed up a scouting patrol, was sentenced to cleaning guns and stocking the armory, the most boring job in the whole base. Of course, this wasn’t helped by the fact that the ponies were currently raiding the base, so he did the most logical thing: arm himself and wait. He wasn’t cut out for firefights at all, constantly anxious, so he simply waited. While he waited for friendly forces or enemies to arrive, he lit himself what he hoped would not be his last cigarette.

Suddenly, the door was slammed through by a gloved hand, completely knocking it out of its shoddily constructed frame. A hulk of a man walked through, wearing futuristic combat armor that was covered with bloodstains. “Oh god oh god oh god oh my god”, He thought to himself, cowering in fear. The massive man turned to face him and simply pointed towards a sign that said: “Armas”. Hugo thought about it for a second, before scurrying off to get the biggest, strongest guns he could remember seeing. After a few seconds, he returned, holding a crate full of guns.

Most of these were massive rifles, with a few LMGs sprinkled in, but one thing caught his eye. An experimental auto rifle, way too big for someone of normal size to wield. He picked it up, with visible effort, and handed it to the absolute monster that stood before him. The man inspected his new weapon, before silently nodding, grabbing some ammunition, and heading out. He paused on his way out, seeing a sawn-off double-barrel shotgun, and grabbing that in one hand, leaving the room with thunderous footsteps.

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“You are nearing a large opening, Slayer,” said Hayden. “I recommend you prepare for battle.”

The Slayer cocked his combat shotgun, nodded, and kicked his way through the door, yet again reducing it to wooden splinters. Before him, he could see human prisoners being chained up and led away.
The nearest pony looked at him and shouted, “HEY I SEE ONE HERE WITH WEAPONS! HE JU- AAAAAAAGH”, before he had his face blasted in. The thunderous shot rang through the room, echoing slightly, and all the heads turned towards him.

With vicious intensity, he loaded up his fresh new rifle, slammed the bolt into place, and started blasting. Ponies everywhere ducked for cover, human prisoners scattered, and chaos ensued. The slayer ran quickly towards his nearest opponent, shattering its pony skull with a gloved fist, and turning his shots towards a small group of ponies organizing an attack. Suddenly, he was hit from behind by an extraordinarily bulky horse, stumbling forwards slightly. He quickly turned around, but it was too late.

The pony had time to slam him again, and he fell on his back. The offending horse leaped on him, wielding a sword attached to its helmet, trying to stab his throat. He gathered his strength before throwing the pony off long enough to get a grip on his recently acquired double-barrel shotgun. As the pony jumped on him again, he shoved the massive shotgun into its maw, blasting the contents of its head into the air in a rain of gore.

After this was dealt with, he dashed forwards into a group of ponies, staggering them with a single shot to the chest from his rifle, and stabbing and slashing his way through attacking troops with vigour. His close call had angered him. Seems he was weakened with the flight into another reality. He noticed that in the back of the room, a few ponies had set up a loose formation, attempting to cast powerful spells.

Before he could open fire, fireballs started to shoot towards him. He dodged most, allowing a few to hit him, and activated the “Full Auto” attachment on his combat shotgun, completely shredding his opponents into not much more than twitching piles of flesh. “Slayer, you are nearing the end of the compound. Between you and your target lies an open field. I recommend an alternate route, said VEGA. “I will mark this on your HUD as well.” The Slayer looked towards his new route, finding a small trap door with a ladder tucked in the corner of the room. He lifted the trapdoor and started to climb down.

He is bathed in complete darkness, the only thing he can sense is the smell of rusty metal and damp wood. The only sound heard, aside from the occasional rat, is his own footsteps. The soft, robotic voice of Haydem rang out in the tunnel, saying “Activating night vision mode, Slayer” before his view was tinged green and he could again see most of his surroundings.

The Slayer marched off into the tunnel after his target, the so-called "Elements of Harmony", preparing to free the earth from invasion for what must have been the 50th time now.

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Air Ace wasn’t doing very well. At first, his troops were destroying these rebels. They had taken most of the facility with very few losses, over 40 captured enemies, and were already expanding the region controlled by celestia’s harmonic magic. Then, the damn armored beast showed up. Every unit he came into contact with was dispatched with insane efficiency. And worst of all? He was headed their way.

The last time anypony had seen him was in the large cafeteria in the human base. Based on magic scans of the building, he was in the sewers. “Damnit…” thought Air Ace, “I'm best at organizing troops for air combat.” Luckily for him, he had a lieutenant he could count on combat-wise. “Blade Dancer, come here for a second. I’ve got an… assignment.”

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The only sound that could be heard echoing through the dark tunnel was the squelch of boots on the muddy earth. The Doomslayer slowly stomped ahead. He slowly reached a small room with a grate on the floor. He walked over and gripped the edge of the grate, slowly lifting it up to open the exit, grinding rust off of the grate. “Slayer, you will need to travel through the sewers for approximately 500 more meters. Afterwards you will reach an exit.”

The slayer paused, then nodded slightly, letting out an affirmative grunt. He climbed down into the open chamber, continuing on through the sewers. After a little while he reached the exit, where a ladder up to a higher level awaited him. He climbed up the ladder, flipped open the hatch, and suddenly, he found himself being lifted off of his feet and flung across the room.

With a resounding crack he slammed into the brick wall behind him, finding himself in a room quite a bit larger than the tunnels before, with actual lights, albeit flickering, dim ones. Before him stood an ambush, a squad of ponies, some with swords, some with horns, all preparing to attack. He was mildly surprised that the horses had swords in their mouths, which seemed like a stupid way to fight, but he saw a few with spiked armor, or blades mounted on their legs.

“QUICK, OPEN FIRE!” shouted a black pony he assumed must be the commander, but his thoughts were cut short as fireballs started flying towards him. He dodged to the side, preparing to rush forward, but the larger ponies wielding melee weapons blocked his path. He rushed forward directly into them, bowling over the first, then finishing him with a shot to the head, then opening fire on the next few ahead of him. A few tried to circle behind but failed. After he took down the first few, the commander, waiting behind the frontline, shouted “TAKE SHIELD FORMATION!”.

In front of him, the ponies with horns began to channel magic and started to form a wall of pure energy. They created a few walls between him and the ponies in melee combat, which seemed to not affect the ponies in any way. They could simply walk through it. He tried to reach through but on contact, his arm hit what felt like a physical wall. He ran around the wall and tried to rush up the ponies’ flank, but concentrated fire from the spellcasters made him take cover behind a pillar. He then decided to activate his shoulder-mounted grenade launcher, shooting a flaming ball of explosives at the shield. After the loud explosion, he ran forward to kill his targets with inhuman speed, but he was blocked. A massive hulk of a pony rammed him to the side, slamming him into a support pillar.

“DIE, YOU EVIL BASTARD” roared the pony, slamming his front legs into the Slayer. The Slayer looked unaffected by the bludgeoning, grabbing the forelegs of the stallion, and holding them away from him. He then activated his shoulder-mounted Flame Belch flamethrower, burning the skin from the stallion’s head. As the still burning lifeless husk fell, The Slayer quickly grabbed a nearby metal pipe and flung it like a javelin at the momentarily unprotected Spellcasters. He managed to hit a blue-and-purple mare in the jaw, immediately snapping the neck. This distraction seemed to weaken the focus of the other casters, and as the magical shield wavered, he revved up his chainsaw, sawing an opening into pure energy.

As he started to push through, the unicorn’s fear of his raw power proved enough to make them lose focus completely and the shield fell. Quickly he dropped down to one knee, as all the unicorns blasted magic at him. He quickly swapped to his Auto Rifle, blasting off all of their front legs in one clean left-to-right sweep of fire. As he stepped forward to finish off the unicorns, the black mare who looked to be in command slashed at him with a blade attached to her foreleg.

As he dodged to the side, he noticed that she kept pace with him as she kept preventing him from lining up a good shot. Thinking quickly, he extended his wrist blade, parrying a few thrusts and slashes with his left hand, while he dropped the rifle and reached back for his shotgun. The mare noticed this, and with a quick flick of her blade, stabbed his unprotected left arm desperately, but this wasn't enough pain to even slow down the Slayer. His arm steadily brought the sawed-off double-barrel to the mare's head, and he blew her skull to bits mercilessly.

After finishing her off, he quickly dashed forward to finish off the brutally maimed unicorns, picking up his rifle and rattling off some automatic fire at the barely crawling ponies, mangling their bodies beyond recognition.

“Well done, Slayer. According to combat effectiveness, the “ponies” stand very little chance against you. Continue onward, as we are nearing your objective.”

The Slayer nodded as he then calmly reloaded, continuing on the path to his target.

Author's Note

Yeah, its pretty bizarre to have the Doomslayer hack-and-slash the conversion bureau universe to pieces, but i had this idea a little while ago. Please criticize me (constructively)