(In this headcanon, Aquaman and Wonder Woman are already aware of the demigods' existence. Wonder Woman is a demigod herself and was involved in the World War, which lead to the pact between the Big Three. As a Royal Atlantean, Aquaman holds Poseidon in very high regard)
"Justice League Watchtower
Diana of Themyscira made her way to the teleporter to head back to earth. Over there, she came face-to-face with Arthur Curry, also known as Aquaman. The Atlantean nodded in her direction, "Diana…"
She gave a slight bow, "Arthur…"
He continued, "If it is not too personal a question, may I know where you are going? Just for the sake of curiosity."
"Long Island, New York"
"Funny story, I was headed there myself."
"Her eyes widened as everything clicked, "You have been summoned as well?
"It seems I have. I wonder why the old centaur has called for us. It wasn't like we were needed for the Battle against Gaea."
"The two heroes soon arrived at their destination and met three figures. One was a bearded man in a wheelchair, the second figure was a man with dark skin, dressed in a trench coat and fedora, with braided hair. The final figure was a barrel-chested grey-haired man with an eye patch.
Arthur knelt and Diana bowed slightly as a sign of respect, "Chiron, Mr. Kane, All Father Odin. To what do we owe this pleasure?"
Chiron's face grew serious, "We have just received a prophecy. It goes like this…"
"An alliance hidden to the world by the Light
"Shall bring both mortal and Godly heroes to fight
"To battle Time with all their might
Foes of the past arise to cause strife
Else the Destruction shall extinguish all life
The two League heroes glanced at each other, clearly spooked. Chiron nodded gravely, "Arthur, Diana, I think it is time we revealed ourselves, at least to the League. Long has the Mist concealed our world from the mortal realm. However, the power is beginning to wane. What has me worried is the line about past foes returning."
Arthur suddenly had a thought and whispered in Diana's ear. She nodded, "I shall have a word with him. The Team needs to be prepared for what's to come. I do not care about his moral code on this occasion. Any potential monsters must be killed."
The Atlantean agreed and chipped in, "Diana, I also think it would be wise if Chiron, Mr. Kane and All Father Odin came with us. If we told the League about this prophecy ourselves, they would most likely dismiss it as ludicrous."
"You have a fair point, Arthur."
Amos Kane interrupted, "I also think it would be best if we brought representatives from both camps, Hotel Valhalla and the 21st Nome. Just give us some time to assemble everyone."
Arthur zeta beamed back to the Watchtower to gather everyone, while Diana stayed behind. After a short while, Chiron wheeled out with around 17 people with him, eight males and eight females, though the 17th hero explained that they were genderfluid and considered themselves as female for the time-being.
Then, the call came from Martian Manhunter, and everyone got engulfed in a bright light. When it died down, they found themselves in a huge metallic building. It also took them a few moments to realize that they were in space! Almost immediately, a blonde-haired girl with stormy grey eyes began inspecting various sections of the floating building and she even took notes.
That lasted until a teenager with dark hair and sea-green eyes, yanked her back, "Annabeth… focus! I know this is a new place, but we do have a job to do."
She blushed profusely, "Sorry Seaweed Brain, couldn't help the architect in me."
Wonder Woman led everyone through the hallways before stopping at a set of doors. She turned back to face the heroes and the mentors, "Wait here, I will call you when the time comes."
Watchtower Meeting Room
All the heroes were making small talk when Wonder Woman strode in. Superman looked up, "Diana… Is everything okay? Arthur mentioned that this was urgent."
She nodded, "It is… Arthur and I were summoned by some old friends of ours, and they had some disturbing news. Tell me, are any of you familiar with Ancient Greek mythology? Aside from myself and Aquaman?"
Batman raised a hand, and he was the only one. The Flash quipped, "Of course Bats knows!"
However, he fell silent after being subjected to the signature Bat-glare. Wonder Woman ignored the banter and recited the prophecy.
She took a deep breath, "What Arthur and I are about to tell you is absolutely secret. Nobody, except for our protégés, must learn about this secret. Long ago, the gods roamed the earth. They were Greek, Roman, Egyptian and Norse. A large majority of them fell in love with mortals and sired children. These children are known as demigods. While we have had our separate battles, they too, have been at war."
Aquaman picked up where she left off, "The mortal and demigod realm has always been separated by a magical entity known as the Mist. For example, a Hellhound from the Underworld will look like a large ordinary dog in the eyes of a mortal.
Wonder Woman's face grew grim, "There is another thing. You probably won't like it, but whatever monsters that appear… They need to be killed."
Batman and Superman shot up in unison, with the former gritting his teeth. He snapped "That is not how the Justice League operates, and neither does the Team!"
Superman added, "I agree with him for once. We are not killers. I'm surprised at you Diana. I would never have thought that you of all people would suggest killing."
However, Aquaman backed up the Amazon, "This 'death' isn't permanent. These monsters are essentially 'soulless'. When a monster is destroyed, its essence is sent back to Tartarus, and it will eventually be reformed."
At that, the two offended heroes began to relax. Superman had the decency to look sheepish, "I apologize… My knowledge of mythology and this demigod world is non-existent. I should have trusted the two of you, especially since you both have Greek heritage."
Batman merely grunted, but Wonder Woman and Aquaman took it as his way of apologizing. Then he spoke up, "We would like to meet these friends of yours."
She smiled, "I had a feeling that you would say that."
The Amazon walked to the door and called out to someone. Soon, three figures came in, the man in the wheelchair, the one with an eye patch and the trench coat-clad man. Aquaman pointed at them in order, "My friends, meet Chiron, All Father Odin and Amos Kane."
At that, Dr. Fate had a look of recognition in his eyes, he took off the helmet to reveal Giovanni Zatarra. The Italian man beamed, "Amos! Is that you, my friend?"
Amos grinned back, "Giovanni! I have been doing well! How is the 10th Nome in Milan?"
Martian Manhunter looked between the two, "I take it, you two know each other then?"
Zatarra nodded, "Indeed, Zatanna and I met him during my travels and we were in Cairo at the time. After Fate, Amos is the most powerful magic user I have known."
Diana nodded and gestured, "Finally, this is Odin the All Father. The three of them can vouch for this prophecy."
Hawkwoman raised a hand, "Earlier, Mr. Kane mentioned something called Nomes, what's that?"
He was only too happy to oblige. The older gentleman said, "A Nome is basically a district or region. The term originated from Ancient Egypt. I actually head the 21st Nome in Brooklyn."
Batman was next, "Chiron, All Father Odin, how many demigods are there, and what are their abilities?"
The centaur glanced at Diana and she nodded. He wheeled over to the door and gestured to some people to come inside. All of them filed inside and one of them stepped forward. He was a Caucasian-skinned teen with dark hair and sea-green eyes.
Aquaman had to resist the urge to kneel before him, instead settling for a nod of respect. The teen spoke, "I am Perseus Jackson, though I go by Percy. I am the demigod son of Poseidon, God of the sea, storms, earthquakes, droughts, floods and horses"
Hal Jordan/Green Lantern could not stop himself, "So, are you and Arthur related?".
"He yelped as Hawkwoman smacked him upside the head and the other Leaguers stifled their laughter.
Aquaman cut in, "If we're going by technicalities, Percy outranks me in terms of power."
He looked back at the teen, "My wife has been dying to meet you. So far, she and I are the only ones who know of your existence. Not even my protégés were aware."
A blonde girl with stormy grey eyes stepped forward next, "I am Annabeth Chase, daughter of Athena, goddess of wisdom, civilization, mathematics, strategy, defensive warfare, crafts, the arts, and skill"
Batman raised a hand, "Correct me if I'm wrong but from what I've read about Ancient Greek myths, Athena was a virgin goddess, right?"
Annabeth nodded, "That's true, but you are aware of how she was conceived, right? The children of Athena were born from a thought… It's complicated. However, goddesses like Artemis and Hera, never sired a child."
Superman caught the tonal change, "Something wrong? I couldn't help but notice the change in tone when you mentioned Hera."
The girl simply said, "She, Percy and I have a bit of a complicated history. Let's leave it at that."
A girl with shoulder-length, spiky black hair, electric blue eyes, in essence a punk look, stood next to Annabeth and Percy.
She introduced herself, "I'm Thalia Grace, daughter of Zeus and leader of the Hunters of Artemis. The Hunters are maidens who have sworn to serve the moon goddess Artemis and are eternally youthful, so long as they do not break their vow to fall in love. It kind of explains why the Hunters and the Amazons get along well. The only difference is that Amazons are allowed to have relationships with men."
Then came a kid with shaggy black hair with relatively gothic attire. Flash joked that he and Batman could be related, earning a signature Bat Glare. He introduced himself as Nico Di Angelo, the demigod son of Hades.
Others included Jason, Thalia's brother and the son of Jupiter. Piper McLean, daughter of Aphrodite, Frank Zhang, the son of Mars, Hazel Levesque, Daughter of Pluto and Reyna, Daughter of Bellona.
An African-American teenager introduced himself as Carter Kane, nephew of Amos and the host of Horus, Egyptian God of war. Then a Caucasian girl with caramel hair and brightly colored streaks introduced herself as Sadie Kane. She is the younger sister of Carter and the host of Isis, the goddess of magic.
Then there was Annabeth's cousin, Magnus Chase, son of Frey the Norse god of peace, fertility, wealth, rain, summer, and sunshine. Next was a girl wearing a hijab, who introduced herself as Samirah-al-Abbas or Sam, the daughter of Loki, God of Mischief.
At Batman's apprehensive look, Magnus was quick to defend her. He insisted that, while Loki was mainly an enemy, Sam hated her father. At that, Batman visibly relaxed.
Alex Fierro also introduced themselves as a child of Loki. They also explained that they were genderfluid. So, for the moment, Alex was female.
Then there was Mallory Keen, daughter of Frigg, goddess of prophecy, marriage, motherhood and fertility. Halfborn Gunderson, a human and an einherjar, Thomas Jefferson Jr, son of Tyr, god of courage, law, and trial by combat
Just as the explanation wrapped up, an alert rang through the Watchtower. Martian Manhunter immediately floated to the terminal. He called out, "I'm getting reports of a bipedal bull-like creature. It is currently rampaging near Happy Harbour"
Batman nodded, "I'll deploy the team. I'm scrambling everyone because we don't know the creature's capabilities."
Percy groaned, "Oh great… it's my old friend Beef Breath! I'll go as backup because I don't know if any of your protégé's weapons will work against it."
Batman stood up and motioned for the demigods to follow him. "Actually, I want all of you to come with me. I'll introduce you to the team. I would also like to know what we're going up against, as well as see your abilities in action."
Annabeth nodded, "Good call! Since we're going to be working together, it makes sense. We can also gauge the abilities of our potential allies."