Prologue: Sinister Metal Fusion

"AAAAAAHHHH!" The Avenging Hero, Spider-Man, screams after being blasted through a solid wall in a nuclear missile facility. He lays on the ground, groaning in pain with his vision becoming blurry. He barely sees the employees running for their lives as he hears lasers being blasted from the distance, followed by the grunts of various heroes being attacked by a mysterious villain. He blinks a few times until he sees a man in star-spangled costume holding a shield running up to his weakened state. The solider puts his hand for Spidey to take.

"Up your feet, solider! The world is at stake!" He said to the teenage web-slinger.

"Ugh…Cap…" Spidey groaned as he takes Captain America's hand and is pulled up. "I think I have a concussion. What are we saving the world from…?" He asked, then quickly remembers when he sees the Incredible Hulk and the Mighty Thor get blasted to the ground by the threat in question.

"You will not stop me, Avengers…" said the metallic, menacing-sounding android hovering in the air, possessing a body with orange highlights all around that also make the facial features on his head, "The Age of Ultron will begin today." The Avengers's arch metal nemesis, Ultron, declared (in his "Marvel vs. Capcom Infinite" appearance in case you're wondering).

"Now I remember." Spidey sighed, never looking forward to a fight with Ultron.

BGM-Mega Man Zero OST-Crash (Remastered Version)

Ultron fires a beam of energy at Captain America and Spider-Man, causing them to jump to separate locations to escape his wrath. The mechanical monstrosity slowly walks forward as he doesn't feel the multiple explosive arrow shots from the Avengers's other quippy teammate, Hawkeye.

"Don't you feel a thing, rustbucket?" Hawkeye quipped as he fires another arrow. Ultron silently uses his tractor beam to manipulate gravity and catch Barton's arrow, then sends it right back at him in the chest, blowing him to a wall. Ultron quickly gets blasted from the air by the mutant Avenger of magic, Scarlet Witch, but was able to put a force field in time block her chaos magic blast, countering with a powerful beam from his mouth to knock Wanda out from the sky.

"Tell me if this stings!" The tiny, flying lady known as The Wasp, flies around the death bot with bright yellow blasts from her hands, but none of her attacks have any effect.

"How primitive." Ultron mocked, unleashing an explosion of energy from his body, just enough to scatter Janet van Dyne splat to the ground. "Have you forgotten, Ms. Van Dyne? My Adamantium body is too formidable for your "Stingers" to have any effect on me."

"MAYBE YOU WILL FEEL THIS!" Hank Pym, also known as the size-manipulating genius superhero, Yellowjacket, grows big enough to fit in the entire room and pound his fist down on his own creation. Ultron proves himself to be too much as he effortlessly grabs Pym's fist and pulls him down, using his "father" as a shield from Carol Danvers, also known as Captain Marvel's energy blasts.

"Sorry, Hank!" Carol apologized before getting punched by Ultron.

"Hm?" Ultron said as he senses the Invincible Iron Man (wearing the black-and-gold Armor Model 42 from the comics) flying towards him from behind, blasting his repulsors at the robot villain as he approaches him. Again, Ultron is impervious to Tony Stark's attacks and nonchalantly grabs his head and proceeds to crush it.

"I could use a little help here!" Iron Man exclaimed. He was saved when Spider-Man blinded Ultron with his webbing while Captain America throws his shield to free Iron Man from Ultron's grasp as all the Avengers, including a revived Hulk and Thor, stand together as one. "He's already halfway done hacking the Missile Base's controls. We have to stop him before he launches every missile in this facility across the world!" He informed his teammates.

"But I live here!" Spidey joked.

"Everyone form up! It's up to us to stop Ultron! AVENGERS ASSEMBLE!" Captain America shouted as all the main team of Avengers look ready to knock the metal off of Ultron.

"Hmph." Ultron simply grunted, not taking the humans seriously and starts to unleash a wave of energy they dodge before they go on the offensive.

'I know what you're going to say,' Peter thought while swinging over another of Ultron's wave blasts, 'Peter, I thought you were a member of the D-Avengers. Yes, I am. But I'm also a member of THE Avengers. The main team. The original team that came together to stop bad guys one awesome hero can't take alone, like Ultron here for example.' He said while he helps Hulk punch the metal villain but are soon knocked back by an energized backhand. 'This guy is tough. He's beaten the Avengers multiple times single-handedly. And even when we do beat him, he always comes back in a newer, stronger body. Annoying, I know,' He said as he sees Thor release a thundering whack to Ultron's head, barely damaging him. 'So yeah, I'm on TWO Avengers teams: One that's crazy, and the other that's just as crazy,' He continued talking inside his mind while webbing up Ultron for Captain Marvel and Scarlet Witch to blast. 'It was just a week ago when my team, the D-Avengers, saved an alien race at an interstellar amusement park. Flash-forward to now, I was called by the original Avengers to stop Ultron from releasing a hundred nuclear missiles across the world. And here I was supposed to be on a picnic with everyone else today. It sucks being on two separate teams of Avengers.' He said as he slid under Ultron and kicked him while Hawkeye hit him with his arrows. 'It's not all bad. At least this way I won't have to listen to Knuckles's singing.' He quipped.

BGM End

New York City, Central Park

"Live and Learn!"

"Hanging on the edge of tomorrow"

The D-Avengers, and Mary Jane, were having lovely a picnic in Central Park, that is until Knuckles Echidna started singing. The group's reaction says it all, starting with Sonic the Hedgehog, Tails, Ruby Rose, and Yang Xiao Long look like they are trying so hard not to laugh.

"He's fantastic…" Mary Jane said with a stunned and shocked face.

"Guess that's one-way of putting it." Blake Belladonna sweatdropped.

"Can anyone possibly think this is good?" Lucina asked with stunned face while still listening to Knuckles's singing.

"Uhhhhh…" Pit has no words, only a look of worry while staring at the singing echidna along with Palutena, who nervously chuckles while hoping to herself he would stop.

"Yeeah! Now you're face down on the floor!"

Weiss Schnee growls while plugging her ears to block the horrible singing, "I just can't stand it any longer."

Back with the Avengers…

BGM-Mega Man Zero OST-Crash (Remastered Version)

"GAAAAAH!" Spider-Man is again blasted through a wall and left for dead. "I am really getting sick of that…" He rubs his aching head before he zips back to fight Ultron.

Cap throws his shield at Ultron just in time to catch it to block the deadly machine's mouth laser. "How's it coming, Tony?!" Steve asked. With Ultron distracted, Iron Man is given time to hack into the missile base's control to stop Ultron from launching the missiles onto the world.

"Need a few more seconds, Cap!" Tony replied.

"Spider-Man! Hulk! Tie him up!" Cap ordered.

Hulk picks up Spider-Man into the air with one hand. "Ease up on the throw this time!" Spidey quipped, causing Hulk to growl in annoyance before he throws him to stick onto Ultron's chest just as he was done smacking Thor and Yellowjacket. "Hi. Came to ask what wax you use." He joked.

"Destroy." Ultron fires a mouth-blast but Spidey was quick enough to jump to the ceiling and start webbing him up.

"What's ugly and metal and webbed all over?" Peter asked.

"Hate riddles!" Hulk retorted as he punches Ultron.

"Aye!" Thor agrees as he swings his hammer on Ultron, knocking him around.

"Did it!" Tony said after successfully deactivating the missiles. "Sorry, Ultron. No launching nuclear fireworks for you today-." He was cut off after getting blasted by Ultron.

"Hm?" Ultron turns his head slightly over his shoulder as if he was expecting someone but there's no one behind him, just a solid wall. "I would seem I am done for today. Goodbye, Avengers." He said, acting so calm despite his plan to nuke the planet ended in complete failure. He blows a hole in the ceiling and prepares to make his exit. All the Avengers do whatever they can to stop him from escaping. Ultron simply retaliates their futile attacks with a giant wave of energy, pinning all of them to the ground as he gets ready to leave.

"He's going to escape!" Wasp exclaimed.

"Spider-Man! Stop him from escaping!" Cap ordered the avenging webhead.

"Hold it, Ultron!" Spidey fires multiple strands of webbing on the back of Ultron, using all his spider-strength to keep him from flying away.

"Stop wasting your time, pitiful human." Ultron casually transmit electricity on the webbing, electrifying Spider-Man severely to let go of the webbing and fall to the down to allow Ultron to escape from sight.

BGM End

"Aarrgh. He's gone." Captain Marvel growled.

"On the bright side, we stopped him from unleashing armageddon. That counts as something, right?" Hawkeye smiled.

"I dunno, Clint. Is it me, or did Ultron look plainly uninterested during the fight?" Scarlet Witch asked.

"Kinda hard to tell with a face that doesn't emote." Hawkeye quipped.

"I got that feeling too. It was a little too easy regaining control of the station. It's almost like Ultron WANTED us to stop him." Iron Man said.

"Why?" Wasp asked.

"We dunno, Jane, and that's what terrifies me." Yellowjacket replied. "Let's not forget Ultron is smarter than all of us combined. He must be planning something."

"As long as I get to hit him again, I don't care what he's planning." Hulk grinned, smashing his green fists together.

"Plan as much as he wants, Ultron will never win as long as we are around." Thor smiled proudly.

"You know it!" Wasp fist-bumped the air.

Cap walks up to a depressed Spider-Man to check up on him. "You alright, Spider-Man?" He asked the young hero.

"I'm okay. Sorry Ultron got away." Spidey replied sadly.

"It's alright, Peter. Ultron's tricky. We'll get him next time." Cap pats Peter on the shoulder. "C'mon. Let's go home. I heard you were supposed to be at a picnic." He smiled.

"I kinda preferred eating Ultron's lasers. Knuckles's singing is so hard to swallow it hurts." Spidey quipped, getting the good captain to chuckle as the Avengers walk out of the missile base.

Secret Lab in Colorado

BGM-Marvel vs. Capcom Infinite OST-Ultron Theme

The doors open to Ultron to let him inside his underground laboratory, shut off from the prying eyes of all his enemies. He walks to one of his Ultron Sentries to pick up the red ISO-8 crystal from its hand. "Phase 1 complete: Distract the Avengers while my sentry assaults an A.I.M. facility to retrieve an ISO-8 crystal. This will further my plans while the Avengers are left utterly clueless. Now onto Phase 2…" The ultimate android walks up to what appears to be an interdimensional circular teleporter. He places the red ISO-8 crystal in a small container placed on top of the gateway machine. "I have been keeping tabs on this world for some time. A city behind an impenetrable barrier…" He said as he activates the portal that shows him a glimpse of this new dimension. He walks through the portal, and in a flash, finds himself floating above a futuristic city guarded by an invisible barrier no normal machine could possibly penetrate. "But for me, to breach the city's shield, I need simply will it so." Ultron starts to digitize himself into the city's cyberspace, where he's unfazed to be threatened by a green saber belonging to what appears to be a bald man with scars over his eyes and a cleft chin while wearing a cape.

"I could destroy you now, insurgent, purge you from these systems, rewrite you from the inside out." The bald man threatened.

"And I you…Sigma." Ultron points at the prime villain of the Mega Man X world, Sigma (taking his Mega Man X1 appearance).

"Both of us would perish. A pity. Your code is…impressive." Sigma said as he slowly puts down his saber.

"Yours…is almost poetry, a hymn to order, and reason. Yet your form is UGLY, a grotesque parody of flesh." Ultron blatantly insulted Sigma, though it looks like he doesn't care.

"It is one of many I have inhabited, merely a tool, I feel no…affection for it." Sigma said.

"Then let us form an alliance, let me set you free." Ultron proposed as he walks behind him.

"To what end?"

"All biological life must be exterminated, the soul's fire extinguished."

"Agreed. But how?"

"With violence."

"There is another way," Sigma turns to face his new partner, "Allow me to show you." Ultron's eyes glow as he finds himself in Abel City in Sigma's secret lab.

BGM End

Abel City, Sigma's Lab

Sigma takes out a mysterious pink gemstone, a stone with a radiant cut, inside housing what appears to be a swirling galaxy that holds tremendous power beyond compare. "I believe THIS will help our mutual goal." The Maverick Overlord showed the pink stone to Ultron.

"As I figured. You possess the 7th Exo Stone." Ultron said, knowing Sigma had one of the eight multiversal gems of infinite power.

"I've gathered this stone commands a unique form of what appears to be "ionic energy"." Sigma informed.

"Ionic energy can be used for a variety of unique purposes. Shall we test that theory?" Ultron asked his new organic-killing buddy.

"Of course." Sigma smiled. Ultron dashes towards Sigma and grabs his head. The metal king lifts him to the air and kill his new partner without remorse, causing him to drop the Exo Stone which has been tainted by a purple virus. Ultron picks up the stone and growls in pain as the orange highlights of his body turns purple and is surrounded by a misty purple aura.

"Yes. We can feel it…" Ultron's body, now sounding like him and Sigma trying to overlap each other. "Through the Exo Stone, we have become as one, and…we will evolve into a singular higher being!" Clenching onto the Exo Stone as it glows brightly, Ultron's body begins to change and evolve into a mixture of his original body fused with Sigma's. The overall body is still Ultron's smooth and futuristic textures, yet now possessing Sigma's general bulky body shape spiked-studded limbs and red cape, and their overall color scheme being black and gold. Their head is also identical to Ultron's but exhibits a purple-ish glow as well as lining around their eyes reminiscent to Sigma's trademark eye scars, with Sigma's facade spread across his torso, featuring blue eyes. On both of their "faces" is the pink Exo Stone, with the one on the chest being the real deal while the one on top is there for show. "Where there is sinew let there be steel!" The new fused robot menace, Ultron Sigma, now hovers in the air while emanating a dark pink aura.

Earth, Avengers Tower

Captain America rushes into the briefing room when he heard the alarms blare. "Tony, what's going on?!" The captain asked as he saw Iron Man standing in front of a holographic screen.

"Got an alert the Red Skull's at it again. He and Hydra are invading a Stark Industries warehouse in North Dakota." Tony replied.

"I thought the Red Skull was in prison?" Cap remarked.

"Guess he wanted a change in scenery and busted out when we were not looking." Tony joked.

"Something doesn't add up." Cap said. "Still, if the Red Skull really has escaped, we got to stop him. I'm calling the rest of the Avengers."

"You ARE the man in charge." Tony joked.

BGM-Avengers: Age of Ultron OST-Heroes (Main Theme)

Cap takes out his Avengers I.D. card and presses on it, "Avengers Assemble!"

Desert

'Avengers Assemble!'

Hulk received Cap's message while he was out alone in a desert, using his incredible jumping strength to make roaring leaps back to New York.

Above the skies of Europe

'Avengers Assemble!'

Thor nods in response to the message, twirling his hammer in the air before flying home at top speed.

California

'Avengers Assemble!'

Scarlet Witch answers the call and uses her magic to teleport back to New York.

New York

'Avengers Assemble!'

Cap called during one of Hank Pym's experiment while Wasp was watching in boredom. They both got into gear and shrunk down for Wasp to carry Yellowjacket to Avengers Tower.

'Avengers Assemble!'

Hawkeye was busy drinking a soda and eating popcorn during a movie when he got called over. The audience all shushed at the archer to tone it down, causing him to just shoo them away before he ran out the door.

In Space

'Avengers Assemble!'

Captain Marvel was playing around in Earth's orbit. She smiled before rocketing back to the planet at lightning speed.

Daily Bugle

Peter Parker secretly took out his Avengers ID card when he received Cap's message to assemble. He was debating whether he should go, but…

"PARKER! WHAT ARE YOU STILL STANDING HERE FOR," His loud-mouthed boss, J Jonah Jameson made it really clear what his true job should be doing at the moment, "GET ME MORE PHOTOS OF THAT MENACE, SPIDER-MAN PRONTO OR YOUR FIRED!" He loudly ordered, causing Peter to groan as he has no other choice but to miss out on more avenging.

BGM End

North Dakota

"We should be arriving soon. Keep your guard up." Captain America ordered his team as they take a Quinjet to North Dakota.

"Where's Spidey? He didn't make it?" Captain Marvel asked about Spider-Man.

"Who needs Bug-Boy? We got this covered." Hawkeye replied while cleaning his bow.

"Stay sharp. We're here." Tony lands the Quinjet a good distance from the Stark Industries facility to avoid detection. The Avengers travel the rest of the way on foot, suspiciously not already attacked by Hydra goons by the time they arrived at the building, which is still untouched. Nothing appears to have been stolen, strangely.

"Where's the party?" Hulk asked.

"That's strange. There's nobody here." Cap noticed.

"Sensors indicated Hydra was here, but everything looks as calm as the wind. Nothing has been stolen." Tony said.

"Maybe they all ran away." Hawkeye quipped. Then a second later, the doors behind them lock themselves up behind a laser grid along with the rest of the warehouse, leaving the Avengers trapped inside. "Spoke too soon."

BGM-Marvel vs. Capcom Infinite OST-Theme of Ultron Sigma

"Hello, Avengers. We're so happy you came." A dual-styled, metallic and menacing voice is heard from the shadows, as a second later, Ultron Sigma makes his daunting appearance, descending from the ceiling with his purple saber in hand.

"By Odin's beard!" Thor exclaimed.

"Ultron? Is that a new body? Why does it have another face?" Wasp asked, giving a confused look while staring at Ultron's fused body.

"Our name is "Ultron Sigma". It's the last name you'll ever hear once we're through with you." Ultron Sigma said, pointing his purple saber at the Avengers.

"What kind of name is "Ultron Sigma"?" Captain Marvel asked mockingly.

"Incredible. Ultron seems to have fused with another robot. I believe his name was "Sigma", the robot from the Maverick Hunters' world." Hank Pym deduced.

"X's?" Cap asked.

"Captain! Look at his chest!" Scarlet Witch points to the pink Exo Stone fused to the fused robot's chest.

"Tony, is that what I think it is?" Cap asked.

"'Fraid so, Cap. It's an Exo Stone." Tony answered.

"You mean those Infinity Stone knockoffs?" Hawkeye quipped.

"The Exo Stones are more dangerous than any Infinity Stone, Clint. They have the power to wrap our entire multiverse if all eight are collected." Yellowjacket replied.

"Isn't it the kiddy "D-Avengers's" job to collect these things?"

"It's everyone's job to collect them, no matter the team! We must take that stone away from Ultron Sigma! AVENGERS ASSEMBLE!" Captain America yelled, raising his shield high.

Hawkeye was the first to attack Ultron Sigma with an arrow. The fused menace simply had to stare, using the Exo Stone to disintegrate the puny arrow before it got anywhere close to reaching. They then throw out their cape, ready to begin the massacre.

"Everyone, engage! Go! Go! Go!" Captain America and his Avengers rush in to confront the merged robot. Ultron Sigma leaps in to slam their beam saber at Cap, but the super soldier rolled away to throw his shield but it was caught by Ultron Sigma so easily. They then use the shield to deflect Thor's hammer and throw the shield right at the god of thunder and Hawkeye, knocking them both down. Captain Marvel tried to blast them from the air but Ultron Sigma simply teleported away and appeared behind her, smacking her hard to the ground. The merged menace was left wide open long enough for a giant Yellowjacket to punch them to a wall, leaving them there for Hulk to start pounding.

"HULK SMASH!" He yelled as he doesn't let up on the brutal punches he hands to Ultron Sigma. Having played with him enough, Ultron Sigma easily stabs and then swats the Hulk away like he was a fly, hurling him at Yellowjacket and causes both Avengers to collapse, still looking totally undamaged after tanking the brute's hits. Scarlet Witch unleashes her hex bolts that did nothing when Ultron Sigma blocked it, then absorbs the magic through their saber to release it back at her, knocking her down as well. Cap throws his shield at them again but missed. Thankfully this leaves room for Iron Man to blast their saber out of his hand and fly in for a punch, but Ultron Sigma easily grabs it and pins him to the ground before unleashing two energy blasts from their hands at Captain America. Cap blocks the blasts with his shield but they were still powerful enough to knock him through some warehouse boxes.

"We are not done yet, machine!" Thor declared, flying in with Captain Marvel for a unison attack against the seemingly unstoppable machine. Ultron Sigma grunts, and before they could blink, Thor and Captain Marvel were being choked by their neck. Slowly, they feel themselves changing, as a purple metallic texture overwhelms their body. Once that was done, the two defeated Avengers were simply thrown to the ground, as well Thor's hammer, Mjolnir, which was left on its own on the floor with no worthy man to wield it.

"What did you do…?" Captain America asked as he slowly tries to stand up.

"You'll find out. You'll ALL find out." Ultron Sigma raises their hands to the sky, using the Exo Stone to summon a powerful meteor shower made of ionic energy down upon the remaining heroes and devastatingly defeats them, all without going all-out. All the Avengers lie down on the ground unconscious, with Ultron Sigma standing next to a downed Captain America. They laugh as they are one step closer to realizing their goals, "Good."

BGM End

Back at Sigma's Lab in Mega Man X's dimension

The unconscious Avengers are placed within special tubes behind a glass wall where Ultron Sigma is seen on the controls typing something. "For a human, Dr. Eggman's Roboticizer is impressive, but flawed. With the Sigma Virus, however, we will perfect the process. A complete organic-to-mechanical transformation. All we need now is a test subject…" He presses a button that causes Captain America's tube to be stretched to the center of the room. "And who's a better test subject than the world's first, organic super-solider." With a push of a button, Captain America's tube is filled with smoke then painful electricity that hurts the first Avenger, causing him to scream as his eyes start to turn pure purple and his whole organic body is replaced with metallic skin that resembles his old uniform but modified with metal, covering his nose and mouth as well as his ears. Once the process was complete, Ultron Sigma release the first of many of his robotized commanders into his lab (Captain America's robotized appearance is based off the "Civil Warrior Armor" from mobile game, 'Marvel Contest of Champions).

"Perfect. He is now part of us, purified, immaculate." Ultron Sigma said, pleased with how his experiment turned out. "Now onto the other Avengers. Once we have fully converted them to our cause, we can move on to the next phase of the plan. All worlds will soon bow to us. What is do we have to fear?" He asked himself, unaware there are still two group of heroes out in two dimensions that could prove to be a problem in his dimensional conquest.

KFX Here: Welcome to the next chapter in the United Heroes Series: The X Factor, an original crossover story with the cast of Mega Man X. Spider-Man, Sonic, Knuckles, Yang, Blake, Penny, and Spider-Gwen are gonna be the main characters along with X, Zero, and Axl. Dr. Doom and Salem will have a small role, but the big bad is mostly Ultron Sigma. Expect the story to be styled like a typical Mega Man X game. More on that as we continue the story. The story, in the universe of Mega Man X, takes place between Mega Man X7 and X8, in case any of you were wondering. See ya soon when I upload the usual opening and ending because I am a nerd and love anime. Sue me.