Disclaimer: I do not own Percy Jackson or the Heroes of Olympus, Supergirl, the Arrow, or the Flash

Story Title: Justice Hearts

AN: This a cross-over between Percy Jackson and Supergirl

Chapter 1:

Earth-819

The second Giant War had ended, but not without a great cost. Percy Jackson, son of Poseidon, the hero of Olympus died in the explosion that defeated the Earth-mother Gaea. His sacrifice ended a war that threatened Olympus and all of humanity. His demigod friends, his mother, and his girlfriend watched with tears in their eyes as the ceremony commenced for the fallen hero. However, little did they know, that Percy Jackson had garnered the attention of a certain creator of all, Chaos. The Creator, not male or female, but a being beyond physical form had claimed the spirit of the fallen hero. Percy Jackson would live again, in another body and on another Earth, Earth-38.

Earth-38, also known as the Alien Earth

Alex Danvers sat at a computer console, monitoring the goings on around the Earth, to her left was Winn Schott, the genius friend of her little sister. Alex sighed. Winn picked up on her discomfort. "She's still that bad, huh?" Winn asked worriedly.

Alex frowned, looking away from her computer monitor. "Yeah, she won't leave her apartment. She took Mon-El's leaving pretty badly."

"Hey, it wasn't like Mon-El had much of a choice, that lead poisoning would have killed him. Your Mom did the best she could Alex, sending him in a pod in cryostasis to the Phantom Zone, it was the best she could come up with."

Alex forced a smile; she knew Winn was right and she would never blame her Mom. However, she was in a dilemma. How do you fix a broken heart? Especially one that was located within a very stubborn Kryptonian. "I'm at my wit's end, Winn. I'm going to have to call Clark, maybe he can help."

"Kara loved him Alex. I don't believe she ever loved anyone like that before," Winn added, his voice low as not to disturb those working around them.

Alarms began to blare throughout the DEO headquarters. J'onn J'onzz appeared within just a few seconds. Winn running through the data on his computer. "Agent Schott, report," J'onn ordered. "Sir, an unidentified object has just entered the atmosphere. Air Force jets could not keep up with the target. It's small and very fast." "Put the readings on the main screen," J'onn ordered. A moment later the energy and other readings appeared on the screen. "Do we have a visual yet?" "On the screen now!"

The viewscreen blinked once before an image of a fiery object streaking through the sky appeared.

"Sir, I have another bogey on intercept trajectory," Alex said. "Any ID on the second bogey?" "Yes, sir, it's Superman." J'onn smiled as he breathed a sigh of relief. "Agent Danvers, prepare a squad to assist. I will accompany you." "Yes, Sir," she replied before hurrying off to gather her squad. "Agent Schott, please keep us up to speed on any changes you register while we are out in the field." "Yes, Sir."

Twenty miles outside of National City

Superman flew three times the speed of sound, but he was still too slow to intercept the bogey that was headed to a large farm outside of the city. He poured on the speed before hovering in the air as the bogey smashed into the ground, but at the rate, it was going such an impact should have been much larger. Instead of a massive crater in the field, only a small crater existed, about a tenth of what it should have been.

Superman landed near the edge of the crater. Smoke filled the depression, obscuring visual contact, but Superman's x-ray vision could see a humanoid, but for some reason, he could not see within the being only its outer shape. He wanted to go down into the crater, but a feeling washed over the last son of Krypton that such an action would be met with hostility, so he waited.

A few minutes later the smoke cleared; Superman's eyes widened at the sight before him. A man knelt on one knee in the center of the crater. He was large, even taller than James Olson. He had black hair that was darker than his own. He was well-built and he wore a costume or uniform. It was skin tight with blue pants, his torso was covered in a red and blue fitted shirt with no sleeves, in the center of the shirt was a black circle with an image of a star shining brightly. He had a cape that was attached to the shirt. The cape was blue on the backside and matched the pants, but the inside of the cape was black with small star-like objects that twinkled like real stars in the night sky. The man stood up and it was clear that he was at least two to three inches taller than Superman had estimated. The man turned to look at the man of steel, his eyes were sea green in color and they glowed like the sun. The man had a golden tan and a slight stubble on his chin.

The man or being hovered in the air before landing just a few feet in front of Superman. Superman's eyes widened; the man looked human. "I am Superman and you are?"

The man looked at Superman up and down before a broad smile stretched across his face. "A Kryptonian, so I must be on the correct Earth."

Superman's blue eyes widened. "What?" He felt stupid with that question, but he was surprised, shocked really.

The man smiled. "Superman, you say. My name is Omega."

"Omega, no offense, but that's a strange name."

Omega smiled. His white teeth shining in the mid-day sun. "Superman seems strange, no offense." Superman chuckled. "My Kryptonian name is Kal-El." Omega nodded in approval. "My name is Perseus Jackson, but my friends call me Percy." Superman was taken aback by the name, it was human, even if the first name was a little old fashioned.

Three large black vehicles pulled up to the crash site. J'onn and Alex raced to the crater, stopping in their tracks at the sight of Superman and the elaborately garbed man that he was talking to. "Superman," J'onn said as he joined the Kryptonian and the stranger. Alex was at his side. Her eyes wide in shock at the man that stood before them. Superman smiled at his friends. "J'onn J'onzz and Alex Danvers, I'd like to introduce you to Perseus Jackson, also known as Omega." "You can call me Percy," Omega added. J'onn smiled at the newcomer, but it was a cautious smile. Percy returned the smile. "Don't worry, I mean the heroes of this Earth no harm. I have come to assist you in the dangers to follow." "That was rather cryptic," Alex quipped. Percy chuckled. "Yes, I assume we can go back to your headquarters for a more formal debriefing." J'onn and Alex were both taken aback. He just offered himself up for a debriefing, no questions asked.

"I can fly and meet you there. I'd like to listen to this," Superman said. J'onn nodded in agreement. "I'd like to fly too," Percy said. The others just stared at him. Percy smiled mischievously. "I can fly. How do you think I made it here?" Superman's eyes grew big once again. "You flew through space with no oxygen or protective suit." Omega smiled. "I need no such coverings or accessories." He gestured toward Superman; the smile never leaving his face. Superman flew off into the air. A golden glow surrounded Percy before he took off after the Kryptonian.

Alex just stared at the sky. "He's hot," she said. J'onn smiled. "I thought you had a girlfriend?" Alex smiled. "I'm gay, not dead." J'onn chuckled as the two walked back to their vehicle before driving back to base.

DEO Headquarters – National City

Superman led Omega through the skies above National City. Omega smiled; he was on Earth again, it had been a long time since he'd seen a city like this, it reminded him of home. His heart ached at the feeling, but he steeled his nerves and resolve; he had a mission to accomplish and a planet to save. Darkness was coming to this Earth, to this Universe.

Superman landed on the balcony at the DEO. Omega landed behind him. As soon as Omega landed a squad of DEO agents dressed in black combat uniforms appeared, guns at the ready.

Superman raised his hands. "Stand down agents, he comes in peace." The agents looked at Superman before lowering their weapons reluctantly. Omega smiled at the agents. He raised his hands to make them feel better. "Superman is correct. I have come to help this world." The agents stepped out of the way, forming a line on each side of the balcony door to the base. Superman led Omega into the headquarters. Omega smiled at the facility. "An impressive facility. A fitting place to defend the Earth from those that would do it harm." Superman nodded in agreement. "My cousin and her sister, the one that was with J'onn, they work here to protect the planet. A few minutes later as they waited in the lobby Agent Danvers and Director J'onzz entered the facility. Omega met them as they entered, extending his hand to the Director. As soon as J'onn touched Omega's hand his body changed into the Martian Manhunter. Omega nodded in appreciation at the green Martian. "I apologize for that, but my abilities must have interfered with your shapeshifting." J'onn smiled, fascinated by the abilities of the being before him. "No trouble at all. My agents know my identity. Now come on, let's go to our conference room and talk." Omega didn't move. The others turned to look at him. "I don't believe this is how you normally meet with unknown beings. I sense that you would like me to go to your med bay." J'onn and others just stared at him in shock. "Are you psychic?" Omega laughed. "No, but I can sense when something is amiss. I do not mean for you to go against protocol. I need you to trust me and if an exam can do that, then so be it."

J'onn smiled at the offer, motioning for Omega to follow him to the med bay. They entered the facility; Alex motioned for Omega to sit on one of the exam tables. He followed her lead, sitting down, his legs still touching the floor because of his height. Alex smiled as she brought over a scanning table and began to scan Omega's body. "Is it okay if I ask you some questions?" Alex inquired. "Of course." "What is your height?" "Six feet and six inches." "Your weight?" "Two hundred and sixty pounds." Alex wrote the information down on her tablet. "What is your species called?" Percy chuckled. Alex looked confused. "What's so funny?" J'onn and Superman stepped on either side of Alex. "No offense, Agent Danvers, but I'm not really an alien. I was once a human or at least part human, but I was completely from Earth, just not this one." J'onn wore a surprised expression. "Can you elaborate?" "I'm originally from Earth 819, or as it is commonly known, the Earth of the gods." "What do you mean gods?" Superman questioned. "On my Earth, I was a demigod; the son of Poseidon and a female human." "A demigod," Alex repeated. Omega nodded. J'onn frowned. "I sense an otherworldly force within you." Omega smiled at the Martian's senses. "Good, it is true that Martians are smart and in tune with their senses. Yes, on my Earth I was a demigod. A Greek demigod who fought to save Olympus and its gods from evil. In the last war I fought I was around seventeen Earth years. I defeated the primordial goddess of the Earth, Gaea, but in doing so I ended my life." "Then how are you here?" Superman asked, more curious than ever about the man or being before him. "My spirit was saved from the Underworld by a cosmic being; the cosmic being." "Rao, you mean," Superman interjected. Omega smiled. "The Creator as I call him has gone by many names and traverses the multiverse, its creation." "It, this Creator has no gender?" J'onn asked. "The Creator has gone by many names and some of those have a gender, to make it easier for lesser beings to understand it's presence. The Greeks called it or him, Chaos, the first Primordial, creator of all. Rao is the Kryptonian sun god, but he is also called Creator. I believe other humans called him God. Martians call him or her the Unnameable One."

The three people before him were completely stunned. This being before them had a connection to the Unnameable One or as some others call it, the Presence. "I see now that you three understand my origins. Chaos freed my spirit, not because he wished to reward me, but because I was needed to save the Multiverse. That mission will begin and end on this Earth. A darkness comes to this world, I know not the details as Chaos is rather cryptic in its explanations."

Alex frowned. "If your body was dead, then how are you here?"

Omega smiled, his sea green eyes alight with immense energy. "Chaos created a new body for me, although it was patterned on my previous one. I became a Primordial god, one sent to help the innocent and the heroes of this world."

"A god, you're a Primordial god?" Alex asked in awe.

"Yes, the Primordial god of stars, in a sense, I am the Creator's son."

Alex wanted to ask more questions, but at that moment she spotted Supergirl, her sister Kara standing outside of the med bay. She excused herself and exited the med bay, greeting her sister with a hug. Kara was in her uniform, but her eyes were red from crying. "You don't have to be here," Alex said. Kara shook her head. "A new alien arrives, I need to be here." "Clark is here, we'll be okay, besides Omega isn't a threat to us." "Omega," Kara said looking into the med bay before her eyes widened at the handsome man on the table. Her mouth hung open. Alex pushed her mouth closed. "You'll catch flies," she said with a hint of amusement in her voice. "You said his name is Omega, where is he from?" Alex smiled, it looked like her sister was fixated on something other than her troubled love life. "Yes, that's just the thing, he's from another Earth and listen to this," Alex began before Kara leaned in closer to hear her sister. "He's a god, the Primordial god of stars." "Rao," Kara said. "No, but from what he tells us, he's the son of Rao or the Creator as he calls him or it."

Kara felt drawn into the med bay after her sister's explanation. She walked in slowly, Alex stepping around her to join the others. "Omega," Alex said getting the Primordials attention. "Yes!" "This is my sister Kara Zor-El, also known as Supergirl." Alex stepped out of the way so Omega could see the Girl of Steel. At first, Omega was fixated on her blond princess curls, so much like those of his lost love. That is until he reached her blue eyes; they were the color of a clear ocean in the sun. His sea green eyes widened for a moment before he was able to compose himself. However, his reaction did not go unnoticed by the others, except for Supergirl, as she too was in a similar situation. Omega reached out his hand. "I am known as Omega, as well as Perseus Jackson, but my friends call me Percy." Kara looked away from his beautiful eyes before taking his hand in hers. "Nice to meet you, Percy."

AN: Just the start of the story, next chapter we will learn more about Omega and his powers.