A.N. = Proper reminder that this is a crossover with an OOC Percy cause I find no sense in making his personality similar to his father, whom he has never met even once before.

Disclaimer - I own neither the Harry Potter Heptalogy or the Percy Jackson Pentalogy.

June of 1979

On the shores of New York's Montauk Beach, the lithe figure of a female who looked like she was just out of school, suddenly appeared with a not so loud crack. Eyes darting around immediately in search of someone in sight, her paranoia was apparent. The darkness of the night made her more anxious, as the faint moonlight created shadows which appeared to move in her opinion.

Taking out something long from her cloak's pocket, she made a complicated gesture and said, 'Homenum Revelio'.

Sighing after a few seconds as nothing happened. She turned towards the sea and gazed at it with a tired yet serene look in her eyes. Reminiscing at the utter hell her entire previous year had been, she took a deep breath as the memories assaulted her mind.

Remembering the school she had graduated from and the friends she had made, her sudden disappearance from the entire Wizarding World except for a few certain times when she had been spotted, the burn marks she had left on her attackers' bodies, all while being on the run from the followers of the strongest Dark Wizard ever.

It's not like she had done anything to the famous dark wizard who went by the name of Voldemort. Her existence as the granddaughter of the second most powerful dark wizard was sufficient enough of a reason for him to send his followers after her.

Under the protection of her school's headmaster, her life until graduation had gone without a hitch. It was after graduation that the attackers came relentlessly. Her talent in elemental charms was a major cause of her survival, although she always tried hard not to burn the other to death.

Gazing at the water of the sea, she tried to calm herself as the memories of the first person she had slain came. Desperate times had led to desperate measures and a deceased person's body for her to deal with.

The flash of light before the spell found its target, the emotionless corpses and the shrieks of pain by the Death Eaters were also the cause of a lot of nightmares.

That was also one of the reasons for her new found love of water. She knew that most of her magic wouldn't work on the ocean. It always calmed her down from her nightmares and brought her solace.

Remembering the large lake her school had and how she and her friends would speculate about the bottom of the lake. Sea creatures and giant squid aside, she wondered if the lake actually had mermen or it was simply a rumour. She should have simply asked her headmaster regarding that, but it was always uncomfortable for her to talk to her grandfather's ex lover.

"The sea's pretty charming, don't you think?"

Turning her head towards the voice around fast enough to get whiplash while quietly grasping her wand, she was met with the sight of a handsome man of around 20 years of age.

A smile adorned on his face and a trident grasped in his hand, he too was facing the sea. Slightly concerned over the trident, she was more anxious over the fact that this unknown, and possibly dangerous, person was able to approach her undetected.

The detection spell she had cast a few seconds ago was one that covered quite a large radius and nobody would have been able to approach her within the seconds she had let herself relax. Even if he had apparated near her, the sound would have given him away. The only thing that was stopping her from cursing the unknown man was that he had made no attempts to harm her.

Mentally frowning at herself for using it, she tried to take a peek into his mind through legilimency. Although it was a piece of dark magic which was milder than most dark magic, she still found it incredibly useful. Its counter in particular was one she relied on a lot in battles. A clear mind in duels was something she found important.

Meanwhile, her attempts to peek into his mind were met with extreme resistance, while the man frowned slightly at her attempt. Going back to smiling towards the sea, he didn't fail to express his discomfort.

"There's no need for that, please. I was simply curious as to why someone was so invested in looking at the sea."

Finally exhausting most of her methods at finding something about the strange person's intent, she tried to approach the situation diplomatically.

"Excuse me but may I know who you are?" Politely yet cautiously, she asked for an introduction. There was no point in offending this unknown person and while she knew she could protect herself, the other man was too unknown for her.

"I go by Poseidon and I am, let's say, similar to you." Replying with a wink, he flashed her a small smile with his lips curling in a way that suggested that he smiled pretty often.

"Like the Greek God?" The woman replied back with a slight confusion. She was used to weird names associated with the Wizarding World, especially after attending a school by the name 'Hogwarts'.

"Yes, like the Greek God, or to be more specific, the god himself." Replying back with a wider smile on his face, he threw out any realistic theory she was starting to create regarding the mysterious man beside her.

"You are saying that you are the Greek god Poseidon?" The woman asked with a confused look followed by an amused smile as the thought of the man beside her acting like a god came across her mind.

Yet, the self-proclaimed god didn't back down from the unspeakable challenge the woman beside him was giving to him.

"I can prove it if you want."

Without waiting for a reply, he concentrated for a second before a water came out from nowhere and took the shape of a horse. The woman watched it with surprise, expecting him to not be capable of such a level of magic.

Though the man was nowhere near finished with his performance. Snapping his fingers with a small smirk as he glanced at the woman's expression, the horse suddenly came to life and started galloping around the beach before standing near the Poseidon and bowing to him.

The woman raised an eyebrow at the wizard proclaiming to be a god and waved her hand in a certain gesture towards the horse as it suddenly transformed to a small rabbit. The magic she had displayed was a complex animal transfiguration on the horse, non-verbally and without a wand over that.

She was certainly a capable witch.

"I can do that too. Does that also make me a goddess?" The woman asked with a cheeky smile on her face, as the man looked at her in surprise before chuckling at her display.

"You are beautiful enough to be a goddess but I don't think you are one. I didn't expect you to be a witch. Then, I suppose that I have to take things up a notch." Poseidon replied with a smile after stopping his laugh. Turning towards the sea, he snapped his fingers, all the while taking pleasure as he noticed the woman's cheek turn slightly red.

Although if it was in embarrassment or at the compliment, he didn't know.

Meanwhile, a small plate with pumpkin pie appeared on his hand after the snap, making the witch's eyes widen in surprise. Finally happy at proving to the lady his true power, he took in the shock on her face with great satisfaction.

"Did that just … but how?" Her shock was apparent from her words. Her surprise was expected as the man had actually broken the entire limits and laws of magic by summoning food out of nowhere. More precisely, The Gamp's law of Elemental Transfiguration which stated that food couldn't be conjured out of thin air.

And the man in front of her had just done that.

"Do you believe me now?" The god asked with a chuckle.

Nodding, she said nothing as she was still in shock. Calming herself down, she looked at him curiously as a few questions came into her mind.

"Does that mean all gods are alive as well?"

"Yes. The gods as well as the monsters are all alive and many of us even visit the mortals down here, especially my nephews, Apollo and Hermes." Pausing slightly, he added an afterthought. "Although the latter is mostly busy with his job."

"Then, how are we not overrun by the monsters?"

"They are mostly killed by demigods like Perseus and Heracles." His face twisted into a frown as he remembered the blasted son of his brother, Hercules. He really pitied his sister for having such a hero named after her.

Seeing her frown, she quietly grasped her wand while wondering if she had done anything wrong and how she would fare against a god with her magic. She was always proud of her magic talent but she felt weak when comparing herself with the god of the Sea.

Seeing her caution, he smiled reassuringly to convince her that she had indeed done nothing wrong. "Don't worry, you did nothing wrong. I was thinking about how different the truth is regarding Hercules' true nature."

Not able to control her inner Ravenclaw's thirst for knowledge, she immediately questioned him about it. "Really? Can you tell me about it?"

Seeing her eagerness, he smiled slightly as an idea came to his mind. "What about we go to one of those midnight cafes and I can tell you about interesting tales like the fight for Athens or the true Trojan War?"

Contemplating the idea for a couple of seconds, she smiled slightly as she realized something. "Are you asking me out on a date?"

"It's a date if you want it to be.'' Replying back immediately, he adopted a mischievous smile as the female opposite him raised an eyebrow at his boldness.

"I will think about that later. Anyways, I heard an interesting restaurant has recently opened somewhere around here. And I am quite curious about the mythological truth."

Smiling at her back, he followed her towards the direction she was leading him too while wondering how he ended up with a 'not-a-date' with… a witch he didn't even know the name of.

Yeah, he could understand why his family sometimes called him slow.

The god of the sea, Poseidon had planned to merely entertain the witch's request for a while before going back to the kingdom and probably never seeing her again.

Unfortunately not all things go as he wanted them to, something proved by the fact that he came back to meet her every evening at the same beach. Their meetings continued like this, with them eventually falling from each other by the end of the month. He would also take a lot of time to finally ask for her name, making her laugh as she introduced herself as 'Sally Jackson'.

Skirting around each other, he finally confessed to her, with her mirroring his feelings and they started dating. Ignoring the fact that he was married and on a binding oath, he continued to meet with her and eventually grew to love her immensely.

He took her throughout the country, taking her to places she had not visited and giving her everything she couldn't experience through her life due to being on the run for almost a year. Their love blossomed smoothly and their dates were fun for both. The relationship was one sweet enough for Aphrodite to be obsessed with.

Their romance was like a flower, growing beautifully. A few months later, Sally got pregnant with his child, something that he was not sure to be scared of or be happy about.

Fast forward nine months later, a pregnant woman in her early twenties laid on a bed in a hospital, mentally cursing the man for the pain she was experiencing, all while she wondered where her lover was.

Unknown to her, a few of her pursuers from a certain dark lord had finally found her after a year of struggle and searching and they were certainly not pleased, to say the least.

A quick and silent disillusionment charm later, one of the death eaters was easily able to get inside the hospital undetected. Silently gazing at the woman he was supposed to kill, he mentally steeled himself for what he had to do. He didn't want to do it but it was the only way to prove his loyalty to his lord.

Pointing his wand in her direction, he whispered something as a flash of green light rushed towards the witch, with her looking at it in horror as she lacked the strength to protect herself due to the tiring childbirth she had experienced mere minutes ago.

Eyes widening, her expression then turned into a rather beautiful and serene expression as she finally departed the land of the living. Tightening his cloak around him, he walked towards the windows as a child's wail reached his ears making him pause midstep.

Turning towards the source of the child, he gave it a petrified look as he realized what the child was and what he would have to do now to complete his mission. Staring at the crying baby, he considered his situation and what he was going to do now. The weight of the situation on him suddenly doubled as he looked at the tranquil face of the woman he had murdered.

Would he choose to lose his humanity by killing the baby or will he ignore it and consequently walk the path of treason?

His expression torn, he shook his head and then turned towards the window and apparated away, mentally giving the child of Sally Jackson his blessing, although he subconsciously knew it wouldn't amount to much.

Meanwhile, the child continued wailing as the nurses finally came into the room to see a dead mother of a child and a distressed child near her. After a swift check by a doctor, the mother was declared dead due to a sudden heart failure after the childbirth and the baby was orphaned from the day of his birth.

One of the nurses would then recount the mother's last words to her with which she had named her child as Perseus.

Hence, on August 18th 1980, Perseus Jackson was born and orphaned according to the Wizarding and Mortal records. And, in the upcoming weeks, the sea would mourn for the loss of a lover while the child would be shipped off to an orphanage somewhere near the coast and forgotten about.

A.N.= How was it? The idea is quite broad and I spent quite a few days thinking on it, before I decided finally to write it.
It's quite different from writing a one-shot, though.
Anyways, do point out any mistakes you might see, and another thanks to Aminta-Defender for the small help in the editing, if he ever sees this by any chance.