Long Long ago, The Devils, The Angels and the Fallen Angel's Great War along with the rampaging dragons was stopped by Azmuth and Grant a Celestosapien, the most powerful being in the universe and the most smartest being in the universe. Grant had created the Boosted Gear by using the Dragons, and Azmuth created the Omnitrix. No one knew the real name but they used to call it the The Great Device but in recent times people got to know the actual name. The three groups had owed their lives to Azmuth and Grant so they granted them a wish.

Azmuth and Grant told the three leaders something. "In a few decades, an Evil Being will take over one of your groups. A boy will come with the Great Weapon. You must obey him and fight along with him. " said Azmuth

"He will help you defeat the Evil Being, and one thing is that he will have full control over a Celestosapein." said Azmuth.

The three leaders gasped as they knew no one in the universe could control a celestosapien. They can destroy the whole universe in a blink of an eye.

The three groups agreed to the wish and they moved on with their lives.

Soon the Gremory and the Sirti household that had moved to Bellwood in USA were to move back to Kuoh Town. 6 year old Rias Gremory and Sona Sitri were playing with their other 6 year old friend Ben Tennyson.

"Hey Ben, me and Sona are gonna love back home, so please don't forget us" said Rias.

"I won't you guys, you were my best friends how could I ever forget you." said Ben

"We won't too Ben, we won't too!" said Sona

Both households had moved back to Kuoh Town in Japan while Ben was left alone.

That same boy became one of the most powerful human beings on earth. He saved the Universe a couple of times. This boy is the wielder of the omnitrix. The Great Weapon. He is a hero. He is Ben 10. The Great One as others that knew about him refered too. The three households of the devils also knew about the Great One but they did not know that they knew him as a little boy. Though Ben don't remember Rias and Sona, Rias and Sona still do.

Now we see Dagon enter the Fallen Angels headquarters as he wreaks havoc and destroys many fallen angels. He throws out Azazel, the Governor of the Fallen Angels and the White Dragon Emperor, Vali. Now they seek asylum with the Gregory Household in Kuoh Academy.

"Rias, the Evil Being has taken over the Fallen Angels and he is preparing to take over the others too." said Azazel.

Rias and her Peerage gasped. As they were told, The Evil Being had taken over one of the three groups, now they just wait for the Great One to save them.

We now see Ben as he is on Galavan as he is talking to Azmuth. Azmuth has explained to him about the Angels, Devils and Fallen Angels and their problem with Dagon.

"Wait, I'm known as the 'Great One', alright, that's sick." said Ben

"Ben this is serious, you need to go to Kuoh Academy where you'll encounter Dagon, he will destroy the world if you don't stop him." said Azmuth

"So do I have to use him?" asked Ben referring to an alien from his Ultamatrix

"Yes, you've completed your training as him so I believe you are ready and one more thing" said Azmuth, "I will give you the code for Master Control,

unlock it whenever you need to using the code."

"Can I get the key for him too" asked Ben as Azmuth nodded.

"So where will I live there and how will I know where to go for Dagon ?" asked Ben

"That's had been prepared, you'll gonna live in the plumbers safe house and you're gonna be a high school student because he's gonna attack the high School." said Azmuth

"HIGH SCHOOL!!! I'm not going to high school, it was a pain in the butt once, I don't wanna feel the pain again." exclaimed Ben

"Ben, Dagon will destroy each and everyone one in this world if you don't go there and besides, you'll stay there for a few days" said Azmuth.

"Alright Azmuth, I will kill that idiot" said Ben as he left to go back to Earth on a plumbers ship.