Amalthea: *cackles evilly* Ok I finally watched the two Percy Jackson movies and read my Harry potter books right after which inspired this story! So please enjoy this Crossover! KON HIT IT!

KON: Amalthea does not own The Harry Potter series, Percy Jackson Series or any songs that appear in this fanfic. All she owns is the idea, Pairing, Family ties and her version of Fem-harry. Please vote in her poll plus Read and review her stories! Now On to SPARTA...I mean...ON TO THE STORY! Enjoy this little plot bunny!

Ch.1

14 year old Marina Potter gasped for breath as she raced to the Wizard bank with Dumbledore and they made it inside just in time, they were quickly shown to a private room with a table and few cozy chairs as the goblin in charge of her account came in and said "We do not have much time, Lady Potter... We must do the test now and get you out of the country due to Fudge's stupidity."

Marina nodded and she quickly cut her palm on the dagger that the Goblin handed her as the blood dripped onto the paper, they watched as words appeared on the paper and Marina Jawdropped as her true heritage was revealed...

Inheritance test for Marina Potter

Father: Poseidon, God of the Sea

James potter: Blood Adopted

Mother: Lily Evans

Inherited powers and abilities:

Animagus: Horse, doe and Water phoenix

Water and Wind elemental

Able to breathe under water

Inhuman Reflexes

Siren like singing voice (when channeling magic into throat)

Affinity for languages

Other relatives:

Percy Jackson: Half brother through Poseidon

Petunia Dursley: Aunt

Dudley Dursley: Cousin

Hades, lord of the Underworld: Uncle

Zeus, ruler of Olympus: Uncle

Marina stared at the paper in disbelief then the Goblin gulped and said "You being a half blood, my lady, seem to make a lot of sense on how you survived..."

"What do you mean Half Blood?"

Dumbledore looked at his adoptive granddaughter and said with a sad smile "it means you're a demi god...they are hard to kill through magic which explains why you've been so lucky in your adventures."

The goblin then spoke up and said "There is a camp in the states where you would be able to live without fear of the ministry finding you. I can arrange for you to be placed as close as possible to it or I can send you to your half brother in hopes no one would look there for you..."

Marina thought about it quickly then nodded as she said "I want to get to know my brother...and if he winds up going to the camp then I'll go too!"

"I understand My Lady; we must get you there soon! Have you got everything?"

Marina nodded as her owl then swooped in and landed on her arm, Hedwig hooted as Marina said good bye to Dumbledore with tears in her eyes then gently took the port key as the Account manager said the password. Marina and Hedwig then stumbled as she landed in the mouth of an alley near an apartment block, Marina looked at Hedwig and smiled as she said "Go fly, girl and be careful!"

Hedwig nuzzled her then flew into the sky as Marina looked at the paper in her hand and realized that it had the Apartment block and Apartment number on it. She sighed in relief and hurried over to the Apartment block as she headed in with her bag and came to the apartment, She took a deep breath and knocked as a pretty black haired woman answered the door and asked "May I help you?"

Sally looked at the familiar looking girl and Jawdropped as the girl said "Are...are you Sally Jackson, Percy's mom?"

"Yes but why are you...here?"

The girl seemed incredibly nervous and said "I'm Percy's half Sister by our dad..."

Sally looked shocked and said "Oh my god...please come in!"

"Thank you..."

Sally quickly got some tea ready for the both of them and sat down with Marina as she asked "How is this possible?"

Marina blushed and said "From what Sirius, my godfather said when I first found out the guy I believed to be my dad wasn't...it was a drunken one night stand after my mom had a big fight with my Step father and dad was upset about leaving his family..."

Sally had to smile as the young girl was kind and polite and she said "for now we'll pass you off as Percy's cousin from England that came to live with us."

"Thank you...Aunt Sally."

Sally smiled and said "I hope you don't mind the couch to sleep on for now...all of our rooms are filled up."

Marina smiled and told her it was fine as they heard suddenly "Mom, I'm home!"

Marina watched as a boy who looked almost exactly like her except with blue eyes and somewhat curly black hair, walked into the living room and paused in surprise. Sally quickly introduced Marina as his cousin from England and then she said "Marina...this is your Cousin, Percy."

Marina stood and said "It's a pleasure to meet you..."

Percy smiled and shook her hand as he returned the gesture; they then started talking happily about their favorite books and movies as Percy sat on the couch with her. Marina was overjoyed to find her brother liked most of the same books she liked to read and said "I'm really glad I came here, Percy..."

Percy chuckled and said "I am too. You're a lot of fun to talk with!"

Marina grinned then noticed Sally was getting prepared to cook dinner and said "Aunt Sally...I'm willing to cook if you want any help."

Sally smiled and said "I'm fine but you can help me tomorrow."

Marina smiled as her and Percy then continued talking...

Two weeks later...

Marina was in the museum with her brother when she noticed the sub that gave her a bad vibe, was taking her brother into an unfinished part of the museum. She quickly followed and slipped into the room as she drew her wand, she watched as the Sub revealed her true form then before the creature could attack Percy and harm him, Marina fired a cutting curse into the creature's side. The creature screamed in pain as Grover and Mr. Bruner came in and she made to attack Marina and Percy, Marina quickly fired off a warning shot with a stunner as she stood in front of her brother with cold eyes looking at the creature.

The two males watched in shock as the new girl easily held off the Fury with her wand, Mr. Bruner then called to the creature and told it to leave before he ripped it to pieces. Marina looked at the two and chuckled as the fury left and then helped her brother up, she watched as Percy was given a "pen" by the older male and they hurried back to the apartment with Grover in front. Marina and the two boys entered the apartment as the man Percy and Sally lived with, then pinned Percy against the wall for disrespecting him. Before Grover could do anything to help Percy, Marina had pulled the man back and broke his nose with a well aimed punch as she snarled "Touch him again and you'll regret it!"

Sally looked amused until Grover said "Sally... It's time!"

Marina, Grover, Percy and Sally were all in the car when Percy kept questioning what was going on, Marina then listened as Percy was told about his father and how he was forced to leave him and Sally. Percy then said "Ok but what about Marina? You used some kind of stick to fend off the fury creature..."

Marina sighed and said "Well I was in training as a magic user in England before the idiot in charge of my headmaster and the school I went to, decided to order me to be killed for something I didn't do..."

Percy blinked in shock then said "You mean Magic is real?"

"Yep, that creature wasn't one I've encountered before but I have faced a Cerberus and lived..."

Grover looked at her in shock as he squeaked "YOU faced a Cerberus and lived?"

Marina nodded and said "I was eleven when that happened..."

Suddenly a cow came out of nowhere and landed in front of the car as they barely missed hitting it but caused the car to flip, Marina groaned in pain as she said "Anybody catch the number of that bus?"

They then noticed something heading towards the car as Grover revealed his true form as a Satyr and kicked out the glass in the window, they quickly got out and ran for the woods with Grover urging them on. They soon saw the gate and ran through only to have Sally hit a barrier before entering, Percy tried to get her through when the creature chasing them revealed itself to be a Minotaur and Marina swore as it caught Sally then it made her disappear into thin air. Marina quickly helped Percy defeat the Minotaur before she caught him from blacking out from killing the creature; Marina helped Grover take Percy to the infirmary where they were met by Mr. Bruner who was in his real form of a centaur. He raised an eyebrow at her lack of Reaction to his form as she then yawned after making sure Percy was comfortable, Chiron then realized how much Marina looked like Percy for the first time since he met her and thought to himself "It can't be..."

Marina looked over at Chiron and smiled as she said "You have the same look my friend Hermione gets when she has a question...What is it that you want to ask me?"

"Do you know who your Godly parent was?"

"I didn't know until two weeks ago...when I took an inheritance test at Gringotts..."

Chiron looked surprised then asked "Who did it show?"

Marina smiled sadly and said "I can tell you already know do to how you look at me and Percy...but where Percy was probably planned, I wasn't...I'm the result of a one night drunken stand..."

Chiron winced and asked "Just how old are you?"

"I'm 14 but I'll be 15 on the 31st of July."

Chiron did the math and winced as he said "It must have been quite the drink to make Poseidon that damn drunk..."

Marina grinned and said "Well from what I found out...he was in a magic user bar..."

Chiron couldn't help but laugh and say "Aye, that would do it..."

Chiron then placed a hand on her shoulder and said "Does Percy know yet?"

Marina shook her head and said "We're going to tell him everything after the museum trip but you saw how that worked out..."

Chiron nodded then said "Why don't you get some sleep, Marina...something tells me you need it..."

Marina nodded as she placed her head on the bed and quickly fell into a light sleep while Chiron covered her with a soft blanket...

Three days later...

Percy groaned as he woke up and Grover asked him what he remembered, Percy told him and jumped as he realized it was no dream like he just thought it was. Just then Marina poked her head in and grinned at seeing Percy wake, She hugged him and said teasingly "Welcome back to the world of the living..."

Percy returned the Hug and Marina took a deep breath as Percy asked "So what's going on? Why were you able to go past the barrier when mom wasn't?"

Marina then sighed and said "Percy do you remember how your Mom hesitated when she said I was your cousin?"

"Yeah...what does this have to do with that barrier?"

"I'm not your cousin but I am still related to you..."

Percy looked confused as Marina then took a deep breath and said "I'm actually your half sister through our dad..."

Percy's and Grover's eyes nearly popped out of their heads at that and then Percy said "But why did you lie to me?

Marina then told him everything that had happened in her school years at Hogwarts and a bit of her upbringing at her aunt's after her mother and stepfather were killed, she then said "we were actually going to tell you after the trip to the museum but as you can see...that didn't go as planned."

Percy smiled and pulled Marina into a hug which she gladly returned then they walked out of the infirmary and they told Percy about where they were and what purpose it served, Percy looked a little overwhelmed at all the info until they went and saw Chiron...

Two hours later...

Marina and Percy were picked for the blue team by a Young man named Luke who was the son of Hermes, Marina grinned happily at hearing the game was capture the flag and was raring to go as Chiron gave the signal to start. Marina quickly followed her brother and Luke past the battle with most of the red and blue team, they were quickly engaged in a fight that Luke dominated and told them to go look for the Flag. Marina grinned evilly as her and her brother then stopped at a stream so Percy could have a drink when she and Percy spotted the Red team's flag, Percy then walked towards it while Marina made sure she wasn't seen. Percy then was attacked by Annabeth and was seemingly defeated as Marina then jumped out in an over head attack, Annabeth was taken by surprise but quickly began to fight back against Marina as Percy made his way to the water and stuck his hand in...

Later that night

Marina laughed softly as she sat in a tree overlooking the party when she noticed the central fire grow much bigger suddenly and revealed a devil like creature that was on fire. She watched as Fire balls were thrown at targets then she recognized the voice of a man who had saved her from her cousin a few times while he visited England, She jumped to the ground and ran over to the creature as she said "Uncle Hads, is that you?!"

Hades froze at that old nickname and turned to the girl who smiled happily and said "I KNEW I recognized your voice!"

"Marina? What are you doing in America?"

"Fudge is what happened; He gave the order to have me killed for something I didn't do...much like how Percy never stole the lightning bolt..."

Hades looked at the girl he had saved so long ago and asked "What were you accused of doing?"

"Murdering Cedric Diggory when it was Voldemort who did it...He somehow came back through some kind of Dark Ritual using my blood, his father's bones and the flesh of a servant doing the ritual..."

Hades and Chiron paled at those words then Hades said "That Bastard!"

Marina looked amused and said "Better not let Auntie hear you swear in front of me yet again..."

The demi-gods all started chuckling at that as Hades said "Don't remind me..."

Hades then talked to Percy quickly about his mother being alive and what he had to do to get her back, Marina and Grover then caught the look Percy sent them as Marina kept herself from grinning evilly. Marina was quick to pack her bag along with Percy and then they made to sneak out when Annabeth and Grover joined them, Marina grinned evilly when Grover asked "How are we going to get to the Underworld?"

Annabeth then led them to Luke as she asked him how his dad would get to and from the underworld...

One hour later...

Marina giggled as Percy and Grover got into a Thumb war to both girls' amusement, Marina then yawned and curled up in her bus seat to get comfy before falling asleep. She was woken about three hours later as they arrived at their first destination and they entered the Garden emporium...