Welcome my friends to my first ever crossover! Ideas for my story will yet again be taken for a short period of time. This story while combine Ben 10 Ultimate Alien/Omniverse with Marvel's Avengers Earth's Mightiest Heroes. I don't own either of these wonderful shows, if I did, I would have kept the animation from UA, and would have kept AEMH going for a little while longer. The Ben of this series will have the new omnitrix, with an Ultimate Alien feature. All Ben 10 characters while have their UA appearances while Omniverse centric characters while have reinvented appearances. So without further ado let's get this party started.

Ben 10: Infinity Chapter I

A Shattered Dream

Four years have passed since Ben received the Neo-Omnitrix, Azmuth's greatest invention, for his courageous defeat of Vilgax. In the following years he had used it to defeat many menaces to the galaxy including, Albedo, Malware, Zs'skayr, and Maltruant, with the help of his friends Gwen, Kevin, and Rook. Now twenty years old Ben is living a charmed but rather boring life, due to an expansion of Plumber influence and addition of new tech courtesy of Azmuth. However he still answers the call whenever his help is needed.

London, UK, June 21, 3:10 GMT

A flash of light and a whoosh of air preceded the appearance of a bright blue portal. A slight droning was heard before suddenly a green and black motor bike shot out of the breech and took off down a cobbled road. The driver barely glanced up as the signature clock tower Big Ben passed by him.

Ben Tennyson had grown up in the four years since his last major battle, now almost a foot taller the young hero wore a brown leather jacket over a green and black shirt, worn cargo pants, and a pair of shin high black boots. On his left arm rested the Neotrix in it's newest incarnation, a white and green gauntlet.

"So Rook, you better have a good reason for sending me across the Pond," Ben said with a slight grin as he shot down the twisting street, "Because I was in the right in the middle of a video chat with Ester."

Rook's face appeared in a holo-screen on the Tenn Speed's dash, "Sorry about this Ben but according to reports from the Plumber outpost around the world several important locations have come under attack. The Vatican, the Louvre, and most recently the Tower of London. Each time an artifact or object of importance is stolen and this symbol is the only clue towards the identity of the culprit.

An image appeared on the screen, it showed a bright red sword surrounded by pink runes. Below the sword, etched into the stone, was the name Tennyson.

"Forever Knights?" Ben asked as he turned another corner and headed towards the spot Rook had marked on his GPS.

"It does not appear to be the case," Rook declared, shaking his head, "All Forever Knights are accounted for and these symbols seem to be made by some sort of magical weapon."

"Well, Charmcaster has been a statue for years so it can't be her." Ben said with a thoughtful expression, "Do we have any other concrete leads?"

"Why not ask an expert?" Rook asked smiling, "There is one other reason I had Blukic and Driba drop you off next to Big Ben and not the Tower itself."

Having reached the marker, Ben parked the Tenn Speed and took a look around. On his left was the London Eye, a massive Ferris wheel, which he smiled up at before glancing to his right.

A small bookstore cafe sat on the corner opposite the Eye. It was painted a light blue and had a very rustic feel. The sign on the front of the building was the head of a black cat with pink eyes next to the words Nine Lives Cafe.

Ben's expression brightened instantly at the sight of the shop.

"Thanks Rook," Ben said into his comm, "This almost makes up for interrupting my date."

"You are welcome Ben," Rook said, "Keep me posted."

Ben walked briskly across the street and quietly entered the cafe, the smells of baking pastries and hot tea hitting him as he shut the door. Looking around Ben realized that the clientele came in all types. In one corner of the cafe sat three Nemunia, which were talking softly while drinking chai tea. Sitting in a chair next to the window was a Tetramand, who held a book in three of her hands and a muffin in the fourth. She seemed to be reading all three books at the same time.

Ben walked past two people sitting in a booth as he made his way to the counter. On the left was a lanky wild eyed man wearing a bowtie and for some reason a fez, while on the right was a pretty young woman with big brown eyes who was looking at the man with a mix of frustration and love.

Ben caught a snippet of their conversation as he passed,

"Isn't this place perfect Clara," The man said with a giddy smile as he sucked down what looked like a shirley temple, "I just love the atmosphere here and on the plus size, they have fezes!"

"Doctor please take off the fez and put it back where you found it." Clara said with an exhausted sigh.

"No, fezes are cool," The man said frowning, "Besides the nice woman behind the counter said I could keep it."

Ben cracked a smile as he walked on towards the counter. He caught sight of the "nice woman behind the counter" and his smile widened. He approached the counter and leaned casually against it.

"Excuse me miss but do you sell smoothies?" he asked

The woman whirled around with a shocked expression on her face as she brushed her orange hair out of her eyes.

"Ben?" Gwendolyn Tennyson said in a shock, she wore an apron over a blue sweater, and dress pants. Gwen looked exactly the same except she had grown her hair out so it hung down past her shoulders.

Gwen to no one's surprise had managed to finish college in just under two and a half years. During that time she had developed into a considerably powerful mage and after completing college she had decided to leave Bellwood and move to England, with Kevin in tow.

She ran around the corner and wrapped her cousin in a hug, before she pulled away and looked him up and down.

"Your hair's a mess." she said critically.

"It's nice to see you too Gwen." Ben smirked.

"What are you doing here?" Gwen asked

Ben looked around the room and then bent down to whisper in his cousin's ear, "Is there somewhere we can speak in private."

Gwen noticed the concern in his eyes as he pulled away and nodded. She turned towards one of the cashiers, "Margie, take over for me please."

The pale blue haired girl nodded and then blushed slightly as Ben smiled in thanks.

Gwen walked Ben to the back of the store to a set of stairs that lead to her and Kevin's loft above. She reached the top of the stairs and snapped her fingers. There was a flash of pink light and suddenly a key shaped like a black cat appeared in midair. It floated down into her awaiting palm, after which she inserted it into the keyhole. The door's surface rippled slightly and then it opened by itself.

Inside was a massive circular library every inch of which was covered in shelves of books and glass cases holding precious magical artifacts.

Ben whistled at the impressive sight of the magical library, "Wow Gwen, this place is incredible, but uh where exactly do you sleep?"

Gwen smiled at the innocent question, "Kevin and I have an apartment near the top of the library next to the observatory."

"Wait you have an observator...ompf!" Ben's question was cut off when a large blue shape tackled him to the ground. Zed barked excitedly as she licked Ben's face covering him in alien dog drool.

"Yes Zed, it's nice to see you too, now please get off!" Ben laughed as the Anubian Baskurr leapt off of him and sat next to a smiling Gwen, who scratched behind her left ear.

"So Ben, you wanted to tell me something important, didn't you?" Gwen said with a quizzical expression on her face.

Ben's grin fell away as he rose to his feet once more, "According to Rook, a thief is stealing important artifacts from all across the world. The most recent theft took place at the Tower of London."

Shock crossed Gwen's face, "That was in the news, apparently someone got in and out of the tower without setting off even one alarm. I investigated the crime scene myself the next day, residual mana covered the entire top of the Tower."

Gwen crossed to the center of the room and began typing frantically away at her laptop, Ben paced around the center dais with a contemplative look on his face.

"Rook had already guessed whomever stole the artifacts had magical prowess, but who could committing the crime?" Ben asked

"Well I locked Darkstar in Charmcaster's old magic bag," Gwen said with a smile as she gestured towards one of the pedestals, "and as far as I know Hex is still teaching at Friedkin, and Adwaita was imprisoned by his former subjects as soon as he stepped foot back in Ledger Domain."

"What about Charmcaster?" Ben asked, "I don't see her little stone thingy around here anywhere."

"Her figurine is sitting on the shelf off to your left," Gwen said without turning around as she investigated deeper into the crime spree, "So you can take her of the suspects list."

Ben searched the bookcase that Gwen had pointed to with his eyes but didn't catch sight of the small granite figurine, "Uh Gwen, did you hide it behind one of the spellbooks or something because I don't see it."

"Ugh" Gwen sighed as she turned around, "It is right there on the second shelf…"

However she was mistaken. Where the figurine once sat a deep red sword had been burned into the wood, with the word Tennyson written underneath.

"She's gone!" Gwen started, "How can she possibly be gone, and why is their a brand mark burned into my thousand year old book case."

Ben frowned, "The same reason it's been burned into the Vatican, the Louvre, and the Tower, someone is stealing important, I'm guessing magical, artifacts. They needed her for something big."

Gwen's eyes shone a bright pink as she turned to look at her cousin, "What was stolen from each location?"

Ben pulled out his plumber badge and activated it's holo-screen, "According to reports a set of ancient granite keys was stolen from the Vatican, a Van Gogh painting from the Louvre, and length of wood that was claimed to be John Dee's magic staff from the Tower of London, and oh here's a new article, someone broke into the Smithsonian Museum and stole the Hope Diamond!"

Gwen's eyes closed in concentration, her hair floating into the air behind her as magic crackled across her palms, "A set of keys, a painting, a staff, and jewel, a key, a painting, a staff, a jewel, a key to open a door, the painting is the door, the staff to perform the spell, the gem to focus it."

Gwen's eyes snapped open and an audible crack was heard, "Someone is trying to open a gate, a connection to somewhere else."

"A parallel universe?" Ben asked excitedly, "Like last time with Maltruant?"

"Most likely," Gwen said with a slight smile as she saw her cousin's whole manner change, "Though they could be trying to forge an artificial link to Ledger Domain."

"Either would be pretty bad though right?" Ben asked as his hand fell instinctively to his wrist, "Hero Time bad."

"Yes and to open a portal with artifacts like these they would need to go to a place where magical energy is abundant." Gwen contemplated.

"And that could be a number of places unless they wanted to go for the real deal and that would leave them with only one place to go." said a gruff voice from behind Ben and Gwen, both of whom turned to acknowledge the speaker.

"Anyone up for a road trip?" Kevin Levin said with a smile as he jangled his keys in front of him.

And there ends part one, yes this chapter is mostly filler but don't worry you get to see some awesome action scenes and tense dimension hopping in the next chapters. Now as you can see I changed up the canon of the main Ben 10 timeline, but to be perfectly honest, this is the third take of this story and I believe this start fits the rest of my story much better. Now as to Ben's romance options in this story I have him set up with Ester now as to after him reaching the Marvel U...I have no clue as of yet. Might have Wasp crushing on him for a while but eh who knows. Remember Vox is swallowing all those flames so stay classy has been Damont Evermore Peace!