This takes place after The House of Hades and Ben 10 alien force. Also Coach Hedge is still on the Argo II (just wanted to include him in the story)

Disclaimer: I do not own Percy Jackson or Ben 10 (wish I did!)

Chapter 1

"Can we please do something fun today?" Ben asked while slurping the last of his lamb and fish smoothie, leaning against the wall of Kevin's garage.

"Or at least drive me to Mr. Smoothies?" he begged. "I already finished my smoothie."

"You already have your own car. Go drive there yourself." Kevin snarled from under his car.

"But my car's at home. I need a smoothie now or I'll die!" Ben whined.

"Tough break."

"You can't let the greatest hero of all times die! I saved the universe multiple times!"

"Can you shut up about that for once?" said Gwen, standing in the doorway holding a smoothie.

Ben's eyes lightened up and he snatched the smoothie out of Gwen's hand. "See? At least someone cares about the hero!" Ben said to Kevin. He took a long draft before his eyes flew open.

"Why strawberry? I wanted wheatgrass and ginger!" Ben wailed.

"Because strawberry is the only normal drink they have at Mr. Smoothies." Gwen replied. Ben sulked, sipping the smoothie. Ben sat on the hood of Kevin's car.

"Get your scrawny butt off my car! I just washed it this morning!" Kevin complained.

Ben slid off the car. "So can we go fight some aliens or something today?" he asked.

"No. I'm going to stay here and fix my car even if the whole damn world is being destroyed." Kevin declared.

"I'm afraid that won't be possible."

Kevin slid from under the car to see who was speaking. He took a breath of relief when he saw it was just Paradox standing there, his hands stuffed in the pockets of his white lab coat.

"Is something wrong?" Gwen asked cautiously. Paradox only showed up in when something bad was happening.

"Yes. I believe the world will fall in a matter of weeks if we do not do anything about it." Professor Paradox stated and Kevin groaned.

"What is it this time? Vilgax? The forever knights?" Ben asked eagerly.

"No. Actually nothing like that. You see, the creatures you will battle against are not aliens. They are monsters."

"Same thing," Ben scoffed.

"Actually, it is not the same thing. Monsters are not from space but rather, from the deepest depths of Tartarus."

"Isn't that just a greek myth?" Gwen interrupted. "The gods don't exist." The sky rumbled, even though it was a clear and sunny day.

"They are as real as you and me." Paradox pointed towards the sky. "And I am afraid Lord Zeus is not pleased of your false statement."

"While you three saved the world from aliens and such, there has been a race of half mortals who saved the world from monsters, giants, and titans. They are called demigods." Paradox explained.

"Yeah, right." Kevin snorted. "That's ridiculous. They're just bedtime stories."

"No, I am serious!" Paradox said, infuriated. "There are actually two races of them: the Greek and the Romans. They have the blood of the gods in them."

"Then how come we never see them?" Ben questioned.

"I and many others such as Hecate were appointed to prevent either side from coming in contact. If they were to meet, I would have Hypnos, god of the river Lethe, wash their memories away."

He took out his golden watch. "But I will say this; we have seven demigods from both Roman and Greek camps working together in a quest. And now they need your aid to get them destroy Gaea's minions."

"We're going to fight Mother Nature?" Gwen asked incredulously. Paradox didn't bother to answer her question; they will all find out firsthand soon enough.

"Come, we are three seconds late," Paradox said, teleporting the three teens elsewhere. Gwen opened her eyes and found herself on board of a flying warship. She grabbed Kevin's hand tightly.

"What the hell?!" A half man, half goat creature yelled. His eyes held a murderous glint as he raised his baseball bat and screamed, "Die!"

Instinctively, Gwen casted a pink shield over their heads as the crazy satyr tried to smash the shield to no avail.

"Whoa! Calm down Coach!" A curly haired boy with a mischievous smile pulled the satyr away. "Guys, we have visitors!" he yelped, and six teenagers immediately came to the deck, golden weapons drawn.

"Who are you?" A dark haired boy with sea green eyes demanded. His three foot long sword looked menacing.

Professor Paradox chuckled. "Now, now Percy. There is no need for unnecessary violence."

"How do you know my name?" the boy snarled.

"Actually, I know who all of you are, and what your fates will be. I am Professor Paradox, a time traveler. I-"

"These people are here to help," a deep voice declared. Gwen turned and saw a human shaped wave rising on the side of the boat.

"Lord Poseidon!" the satyr exclaimed.

"Dad?" Percy asked. "I thought all the gods were not allowed to come in contact with humans anymore?" He lowered his sword and everyone else followed his motion.

"Percy, you've must have noticed that several gods have helped you so far. About time I do the same." Poseidon chuckled. "They are your allies, and they will help you defeat the giants and Gaia."

"How?" one of the teenagers asked, but Poseidon sunk into the ocean. Gwen had also noticed Paradox had also disappeared.

"Yeah…this is awkward," said Ben, rubbing his neck.

"I don't trust them," the satyr said gruffly.

"Well, Poseidon said we could trust them!" A pretty girl with choppy chocolate hair and blue eyes scolded. She offered to Gwen. "Hi, I'm Piper."

Gwen shook her hand. "I'm Gwen."

Piper gestured at her friends. "That's Jason, Frank, Hazel, Annabeth, Leo, and Percy." She seemed cheerful and friendly enough.

"This is Kevin, and that's my cousin, Ben." Everyone exchanged awkward waves and nods.

"Are you demigods?" Annabeth asked.

"Um…no?" Kevin replied.

"But you can see through the Mist," Jason pointed out.

"We're not half god," Ben tried to explain. "We're half alien, half human."

Leo began to laugh. When he saw everyone else's serious faces, he asked weakly, "For real?"

Before anyone could reply, the boat lurched forward. They all grabbed the railings. "Damn it! What is that?!" Leo screamed.

The slimy tentacles wrapped on the wooden mast before snapping it. "That's the fourth time it broke!" Leo wailed.

He burst into flames and bravely grasped onto a tentacle. The monster shrieked and recoiled, shaking Leo off.

Gwen caught him with a manna panel before he fell into the water. "Thanks," he said.

"Duck!" Gwen yelled, pulling Leo to the ground before a tentacle could sweep them into the water.

"I take it back," Kevin smirked. "I do feel like fighting something."

He snatched Jason's gold sword and absorbed it, shielding his body with Imperial Gold. He whistled, "Nice," before tossing the sword back to a dumbfounded Jason.

Suicidal as usual, he lunged straight at the creature. The octopus merely flung him away into the water.

"It's hero time!" Ben yelled, slamming the ultimatrix. In a flash of green, he turned into Jetray. "Jetray? I wanted Humungousaur!" he whined. "Stupid watch," he muttered darkly before flying off.

Ben shot lasers at the octopus-like creature while Frank turned into a gryphon. Ben had to admit that was awesome since Frank didn't need a watch or something to change. Frank raked the octopus' eyes with his claws.

The rest of them jabbed their knives and swords through a tangle of tentacles, running on Gwen's manna panels. Percy easily stabbed the monster in the left eye before he was thrown into the sea.

"Leo! Get the Greek fire!" Hazel yelled.

"I can't get a good aim!" he yelled back. He looked desperately into the maze of tentacles.

"Maybe I can!" Ben yelled confidently and grabbed the jars from Leo's arms with Jetray's feet. He flew up before diving down to the creature's mouth.

Before he could drop the jars, the giant octopus closed his mouth. "Ben!" Annabeth yelled.

They stood there stunned until they saw a flash of green coming from inside the stomach. A black, yellow, and white colored ball flew out of the mouth and landed on deck.

Ben transformed back. "That. Was. Disgusting." Ben shivered.

The giant octopus screamed guttural shrieks as smoke fumed from its throat. Slowly, it sank back into the depth of the ocean.

The teens cheered until Annabeth asked, "Where's Percy?"

As if he was on cue, Percy stood on a wave holding the collar of an unconscious Kevin, but strangely only Kevin was soaked wet.

"Kevin!" said Gwen worriedly as she rushed to him. Kevin's eyes fluttered open and he smiled at Gwen. Gwen hugged him and kissed his cheek. She whispered a spell that dried the salty water off of Kevin.

Annabeth's arms tightened around Percy as she whispered, "Seaweed Brain." Percy grinned as he hugged her back.

"We make a pretty good team," Jason said.

"Yeah, I guess we do." Ben said happily.

"One reason why we should stick together," Annabeth said, studying them with her stormy gray eyes.

"Pizza anyone?" Leo asked cheerfully.

"Do you guys have smoothies?" Ben asked excitedly.

"We got magical cups that fill with whatever you want. Nonalcoholic, of course."

Ben's eyes lightened up. "Count me in!" he said before dashing below deck with Leo and Kevin.

Gwen, Hazel, Piper and Annabeth all rolled their eyes at the eager boys.

Review and I'll give you a virtual cookie! Also if you want a character or monster to be in this story please tell me!