Disclaimer: I don't own Percy Jackson or the Avengers.

The sun was shining above Camp Half-blood. The blue sky was cloudless, and happy campers sat chatting amongst their siblings while they ate their lunch in the Pavilion. Overall, your average day at Camp Half-blood. That is, until seventeen year old Nico di Angelo shadow-travelled into the pavilion. He looked paler then usual and shocked, both of which did not go unnoticed by his older cousin Percy Jackson.

"Nico," Percy said, concern evident in his voice. There was not much that could freak out Nico, Ghost King and resident of the Underworld. Whatever was wrong had to be serious. "What happened? Are you alright? Did someone die? Why are you holding a Smurf?"

Nico tossed away the offending Happy Meal toy and started to speak as fast as he could. "I went to McDonalds to get a Happy Meal, and thousands of creepy-assed lizard aliens just invaded New York through this giant-magic-glowing-blue-space portal thingy and now they're flying around on these high tech jet skis and attacking mortals and the only people fighting them of are those 'superheroes' and that godsdamn Asgardian." Nico blinked. "I think that's it."

There was silence until Chiron surged to his feet (hooves?) and yelled "DEMIGODS! TO ARMS!"

Demigods sprinted in every direction, to their cabins, to the armoury, to the stables, all getting ready for battle. Nico ran with Percy to the Big Three's cabins so they could grab their armour. Percy entered the Poseidon cabin and donned his armour at record speed. He also grabbed a bag of Ambrosia and his flask of Nectar, then made his way back outside. He found Nico garbed in the black armour he had worn in the Battle of Manhattan. The skull helmet was still as terrifying as ever. Percy sighed in relief when Nico flipped up the visor. Nico gave him a half smile.

"If it still freaks you out after four years, think what the enemy's reaction is going to be like."

Percy grinned back and they quickly made their way to the Athena cabin. In times of battle, the Athena cabin was the place to be. Upon entering, Percy made his way to Annabeth, who was in the middle of discussing the best place to launch their attack with her half-brother, Malcolm. Percy gave her a quick kiss on the cheek before she turned to Nico.

"Where is the portal?" she asked.

"It's above that piece of crap, Stark Tower," Nico replied, "I saw it open when I was leaving McDonalds. A blue light shot up from the top of the tower, so whatever made the portal must still be on top of it. That's where most of the lizards were, so I think that's where we should head."

Annabeth nodded in agreement. "Alright, all demigods to Stark Tower. Move out."

Percy smirked. "I like how no one even bothered to doubt Nico, even when he appeared in the middle of lunch, yelling about aliens, while holding a smurf." Nico smacked him upside the head.

"Shut up, Seaweed Brain."

An army of forty demigods was just about to mount their pegasi or shadow-travel to the city with Nico, when a flash of light signifying a god's arrival lit up the air. Lord Hermes stood before them, dressed in his tracksuit and holding his mobile phone.

"Stop," he said, "You cannot go any further. We have decided that the demigods are not permitted to become involved in this battle."

"What do you mean we're not permitted to become involved?!" Clarisse yelled angrily, "You were all pretty eager for us to fight last time New York was under attack."

Hermes shifted uneasily. "I'm afraid we can't risk it. The mist still has yet to fully recover from the Titan War, and what with these Asgardians battling in full view of the mortals, if demigods were to become involved, there is a high risk that we will be discovered. That would be a disaster."

After hearing this, Clarisse became even more incensed. "So, what? You're just going to let thousands of mortals die so we can continue to live in secrecy? That's a coward's way out! We are heroes, not cowards!"

The other campers yelled in agreement. Her words had hardened their resolve.
Hermes rubbed his eyes tiredly. "If it makes you feel any better, I voted for demigod involvement, but it's out of my hands. The council has made its decision. We will just have to wait out this battle and hope for the best." He disappeared in another flash of light before they could argue any more, and the demigods present averted their eyes, so as not to be incinerated. The majority of campers began to wander off, back to their cabins to wait out the invasion, not daring to defy the gods. A few stayed behind. Percy, Nico, Annabeth, Clarisse, Connor and Travis Stoll, Will Solace, Chris Rodriguez, Jake Mason, and a son of Hecate.

"Well," Nico said, in the silence that followed, "I, for one, don't plan on staying here and doing nothing. I'm going, whether the gods want us to or not. A small group will hardly reveal the existence of the gods to the mortals."

"I'm going too," Percy announced. "Annabeth?"

"Count me in," she said. The other nodded in agreement. "Nico, can you shadow-travel all of us to the city?"

"Yeah," he nodded, "But I'm going to need Ambrosia when we arrive. By the way," he said to the son of Hecate, "Who are you?"

The boy grinned, "I'm Elliot, just got here last week. My dad lives near Stark Tower," His face grew serious. "He might be in danger, there's nothing the gods can do to keep me away."

"Alright, good enough reason," Nico said, and closed his eyes.

"Uhhh, Nico?" Percy asked, "You need us to find some shadows?"

"Don't insult me, Seaweed Brain, I'm not an amateur." He grinned darkly, "I'll just make my own."
A wall of darkness rose up out of the ground, and they were engulfed in shadows.
Almost instantly, the shadows spat them out into an alley on the street opposite Stark Tower. Only Nico was left standing.

"Oh gods, that was horrible," Connor groaned from the ground. Nico snorted in disdain.

"Wimps," he muttered and then proceeded to scarf down a square of Ambrosia. He looked out the entrance of the alley as he waited for his strength to return. The sky was full of alien vehicles, and the ground that wasn't burning or covered in rubble was serving as the battle ground for the alien troops and the mortal cops. Nico cursed as he watched a police officer get shot by one of the aliens. He was killed instantly.

"Get off the ground," Nico said over his shoulder, "I'm going on ahead. When you guys are able to walk, feel free to join in." Nico then ran from the alley towards the battle. He unsheathed his sword as he went, and a feral snarl appeared on his face. Time to teach these aliens a little lesson in death.

To say Nico di Angelo was tired was an understatement. He'd been fighting for the past hour straight, summoning horde after horde of undead minions, using the shadows to rip the aliens to shreds, and creating chasms in the ground that sent his enemies directly to Tartarus. Unfortunately, it was taking its toll.

"Percy!" Nico yelled, "You still alive?"

"More alive than you, Death Breath!" Percy replied. Unlike Nico, who was sporting a number of wounds, Percy was fine. The Curse of Achilles saw to that, but Percy looked just as tired as Nico. They were giving it everything they got but the aliens just kept on coming.

"We need to find a way to close that godsdamn portal," Nico yelled over the noise.

"There's no way we'll be able to get to it with all these aliens in the way. Maybe we should-" Percy was silenced when a red, metal blur zoomed above him, shortly followed by one of the huge monsters that had come through with the alien attack force. Nico wasn't sure whether to call the aliens monsters too because they could be harmed by celestial bronze. They were quite lucky. They hadn't considered if the aliens would have the same resistance to celestial bronze as mortals did.

"Percy! Nico!" a male voice called to them.

"Is that Elliot?" Percy asked. Nico didn't' bother to answer, just ran towards the voice, slashing and stabbing any aliens who got in his way. They found Elliot locked in vicious battle with one of the alien lizards. He had managed to disarm it and he still had a dagger, but the thing had still had claws and armour. Elliot already had cuts covering his arms and the right side of his face. Nico didn't bother to notice anything else. He just clenched his fist. Shadows rose from the ground and lunged forward, shooting straight through the alien. It fell to the ground dead just as Nico arrived beside Elliot, who had collapsed. Nico quickly fed him some Ambrosia and poured some Nectar over the deep wounds on Elliot's arms.

"Thanks, man," Elliot said, wincing as he sat up. He turned to Nico and looked at him intently. "I have an idea, and if it works, we'll be able to kill all the aliens in less than a second."

Nico frowned at him in doubt. "Whatever your idea is, it has to be better than us fighting thousands of aliens by ourselves. What is it?"

Elliot gulped, "Well, as you know, my mom is Hecate. She's the goddess of magic. I'm pretty good with magic but I'm nowhere near as good as my siblings. When I asked my mom if there was there any way for me to get stronger, she said that some of her children were able to combine their powers with other demigods, and that I might be able to do it." Percy arrived beside them, panting heavily.

"Whatever it is you girls are chatting about, hurry it up. I can't hold them off much longer, and we got about a hundred more lizards incoming" he sighed heavily, "I'm beat." Nico glanced back at Elliot.

"Combine powers, huh?" His eyes widened in realisation. A grin spread across his face. Percy looked at him nervously.

"Dude, whatever it is you're planning, do it fast. You smiling is creeping me out more than the army of lizards." Nico held a hand out to Elliot and helped him to his feet.

"What do we need to do?" Nico asked.
Elliot took out a piece of chalk and started to draw a circle around the body of alien Nico had just killed. He then began to draw a mixture of symbols and Greek words for death and magic.

"I didn't want to try this unless it was a last resort. It might not work, I'm not positive what's going to happen, but if it does work, it will kill every single alien in the range of the spell. Its range is about the size of the city if we put enough power into it. Are you willing to risk it?" Nico gazed at the city that was burning around them, being destroyed by the invaders.

"Yes" Nico replied, "Tell me what to do."

Elliot finished drawing the circle, and he then held his knife up to his arm and cut a shallow slice, wincing as he did so. He then handed the knife to Nico, who sliced his own arm open without hesitation. They then stood on opposite sides of the body and clasped hands, their wounds dripping blood onto the body.

"Focus on your powers over death," Elliot said, face clenched from the pain, "Use your powers for removing a soul from a body, but focus it on the circle." Nico raised an eyebrow but complied. Shadows began to curl around his body, and he began to emit a deathly aura. Elliot began to chant in Ancient Greek, and the body began to glow with a white light.

"Ummm, I'm guessing it's a little too late to ask what's going on?" Percy asked. The others ignored him. The deathly aura continued to grow until Percy started to find it hard to breath. The body began to glow brighter and brighter, and suddenly, a nuke flew over head. Percy had just enough time to gape like a fish before it disappeared into the portal.

"What the-" He was cut off by the sound of an explosion. The portal began to shrink and just before it fully closed, something red fell through. Just as it did, whatever Nico and Elliot were doing took effect. The dead body exploded, and Percy watched in awe as all the aliens in view dropped to the ground, dead. Nico collapsed to the ground along with them, and Elliot staggered away from the circle. Elliot looked around and then started a victory dance.

"WE DID IT!" he yelled. Percy just shook his head and ran to Nico.

"Hey, Zombie Dude, wake up!" Percy was scared until Nico groaned and began to curse Percy in Greek and Italian for waking him up. "With great power, comes great need to nap, you said. Too bad, Death Breath, we gotta get back to camp, and we need you to get us there." He then slapped Nico in the face.

"What the Hades!" Nico yelled groggily, as began to wake up. Percy dragged him to his feet and helped him limp back to the alley where they first arrived. It took them a while, so by the time they arrived, the others were already there. They were injured, but nothing to serious.

"What happened?" Annabeth asked as she took in the snoring Nico, and the happy dancing Elliot.

"Why did all the aliens spontaneously drop dead at the same time?"

"Nico and Elliot did some sort of magic spell and it killed them all," Percy said, as he tried not to fall over under the combined weight of his exhaustion and an unconscious Nico. "We'll explain it once we get back to camp." The others agreed, and Percy slapped Nico again.

"For the love of Zeus, STOP SLAPPING ME," Nico yelled, glowering sleepily. The fact that he could barely open his eyes nullified the glare.

"Then stop falling asleep," Percy replied, "We need you to bring us home, can you manage it?"
Nico got to his feet unsteadily. When Percy tried to assist him he shoved his hands away. He could stand by himself. He was really tired but luckily the alley was enclosed in shadows, so Nico didn't have to make his own. With great effort, he shadow-travelled them back to camp. Upon arrival, he had just enough time to see the angry faces of all 12 Olympians, before he passed out again.