A/N: Yo! This is my new Ben 10 and Marvel, as well as DC universe crossover. I have created this due to an idea that I got.

The idea is this: No one can transform their DNA that quickly and back without any permanent changes. What if, the omnitrix blocked out those changes when it was on? What if, when Ben took it off, the changes appeared? Ben/Harem Darker Ben Powerful Ben

This Ben shall have the powers of the aliens he could transform into, with some limitations.

Ben's powers:

For the first year or so, Ben will only be able to do minor stuff, spit goo, echo location, local transformation into element, and solar absorption.

He can only use one power twice per day (goes up later)

He can only use one power at a time at first (goes up later)

Disclaimer: I don't own Ben 10, DC universe, or Marvel.

Chapter 1

"Are you ready for this, Ben?" Grandpa Max asked his grandson.

Ben was fifteen at the moment and had a bit long hair and green eyes. He wore a short sleeve black muscle shirt and tattered jeans.

His Grandpa wore an orange Hawaiian T-shirt with denim shorts.

They were currently cutting off the omnitrix, or, at least, making the final preparations to cut it off using alien tech.

"I'm fine, grandpa," Ben reassured his grandpa.

His grandpa wore a small smile as he got the saw ready to remove the omnitrix.

Ben's grandpa nodded and placed a mask over his face in order to stop the sparks from hitting him.

Ben was fine since his arm was encased in a rare alien element that was said to be unbreakable once it was forged.

"Let's do it," Ben said, working up the courage for a few seconds.

Grandpa Max nodded and lowered the alien saw to the omnitrix, letting it cut through it until it was completely separate.

Ben let out a small smile due to the fact that the procedure had been successful.

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Elsewhere, a small alien creature let out a quiet, "oh dear."

It appeared that the omnitrix's failsafe had fallen.

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Ben woke up the next morning and felt a bit colder than usual.

He looked in the bathroom mirror when he went in there to get ready for the day, and was surprised to see that his skin had a reddish tint and it looked like he had gills on his neck.

Ben let out a quiet gasp before looking for something to cover his neck up until he could see his grandpa about it.

He found a scarf lying nearby and decided to place it on top of his neck and then wore his jacket. It was winter break so no one would question the need for a scarf and jacket.

Ben placed it on and then went downstairs for a quick bite to eat.

His parents weren't down there, so it was easy for him to avoid any type of questioning as he quickly got out of the house and went to his grandpa's RV.

"Grandpa," Ben called out.

"Hey, Ben, you're just in time to try some of my Buttered flounder eggs." His grandpa said.

Ben shuddered; he didn't even want to think about what that would taste like.

"I don't have time; I need to talk to you about something." Ben said urgently.

"What is it, Ben?" Max said.

"This," Ben said as he removed the scarf and showed the gills to his grandpa.

"Hmm, while it is surprising, this has happened before, remember?" Max said as he examined the gills on Ben's neck as well as the reddish tint.

"I'm afraid that is not true," A cultured voice said from below them.

Ben looked down and was surprised to see Azmuth down beneath him.

"What do you mean?" Ben asked.

"I mean, that when you removed the omnitrix, the failsafe was also removed." Azmuth said in a grave voice.

"Failsafe?" Both Tennysons questioned.

"Yes, see, there was another reason that the omnitrix was not meant for use like Ben has been using it. That reason is that it is not 100% safe." Azmuth said.

"What do you mean?" Ben asked nervously.

"I mean that there is a cost to extensively changing your DNA like you have been." Azmuth said.

"What is it?" Ben asked.

"The cost is that your DNA starts to intermix with the DNA in the omnitrix, all of it. The failsafe was there to prevent it from occurring as long as the omnitrix was on you. However, now that it is off, the entire DNA in the omnitrix has intermixed with yours. You essentially absorbed the power of the aliens, as well as the faults." Azmuth said.

"I don't really see the downside." Ben admitted after a few minutes of thought.

"The downside is that there are physical changes as well!" Azmuth snapped. "You literally cannot go back to being normal now."

Ben looked shocked at that before he scowled and charged at Azmuth again.

Azmuth looked at Ben furiously before he tapped his cane on the floor, causing Ben to disappear in a flash of light.

Ben reappeared in the streets of where he was then and scowled as he walked off and looked to see if there was anything that he could recognize while he was there.

He saw a sign that said welcome to Bayville and looked up at it curiously.

He recognized the name and he knew that it was the base of the X-men, but he didn't know what would happen there.

Ben walked through the streets as silently as he could and slipped into a Café.

There, he saw a lot of empty seats and sighed as he got in one of them and sat down and thought about how his life had went down the drain in the last few weeks, starting with Elena and going downhill from there.

Done! I hope that you all enjoyed the preface to this. Please read and review!