A/N: What started as a simple idea for a nice sized one shot ballooned into a multi-chapter story. Big thanks to my beta/editor Carmel, who provided guidance to shape this story into its best possible form.

Assume regular canon for the Harry Potter and Percy Jackson series unless otherwise stated, including dates and years.

Helen Potter and the Goblet of Fire

I.

The Great Hall of Hogwarts rumbled with a rare excitement, even for November and the traditional start of the Quidditch season. Harry Potter felt as if he was at the eye of the storm and it wasn't because of the lightning bolt scar upon his forehead. It was because his twin sister, long thought missing, was finally coming to Hogwarts. A few days ago, he had been so caught up in the excitement for the Tournament and the arrival of the foreign students that she had slipped his mind. It was odd, he would admit to Ron and Hermione, given that he often thought of her ever since Hagrid had revealed her existence to him all of those years ago in that hut out at sea. Helen Alexandra Potter had been delivered to the Dursley's with him in the aftermath of their parent's murder, yet at some point in the night she had vanished. Now he would finally get to meet her, to know that she was more than words on a page and a few pictures of giggling babies.

Just wish it weren't because of this bloody tournament. Would she even have to participate if she was at Hogwarts? The school, along with their guests from the continental schools of Beauxbatons and Durmstrang, had been shocked when a fourth name had emerged from the Goblet of Fire on Halloween. Harry had tensed, a terrible expectation at the back of his mind, ready to stand. Be it troll, snake, or godfather, his year at Hogwarts was defined by an event on Halloween. He suspected it had to do with Voldemort murdering his parents on that day, though it could be a coincidence. Instead, Dumbledore had stared at the slip in his hand for several seconds, as if it answered a dozen questions. Eventually, Professor McGonagall got his attention and he softly announced, "I never thought I would say this name again.

"Helen Potter."

Today was the Third of November and Helen had arrived in country that morning. It was a tremendous shock for Wizarding Britain, learning she had arrived by 'aereoplanee' and was accompanied by five girls, most of who appeared to be younger than her. Only one, identified in the article as 'Zoë Nightshade,' appeared to be an adult. Harry had debated with Hermione and Ron whether the girl's name was right, given The Daily Prophet had a habit of misnaming people without serious influence in Britain.

"Oh, it probably is," Hermione had said, frowning at Ron's snort. "American witches and wizards have unusual names, even compared to here."

"Buff daf naw trew," Ron protested. Hermione turned to Harry, frowning. The Twins had slipped him…something at lunch.

"Ron said, 'but that's not true.'" He glanced at his best friend, and with a smirk, added, "Honestly, I thought the same reading through A History of Magic before coming to school."

It was the wrong thing to say then, for Hermione had begun a tirade about, "Why didn't you keep reading your books," and "You have such potential Harry, I don't understand why you seem to waste it."

He headed off a lecture, but the frown Hermione shot Harry promised the conversation wasn't finished. As they waited, the gossip and chatter grew louder. Ron, his tongue finally unstuck, had begun to grumble about the lack of food when the doors opened with a loud groan.

The woman from the Prophet, Zoë, entered. Unlike the parka from the photo, she was dressed in silver Greek armor, a fine black cloak flowing from her shoulders, and a glimmering helmet in hand. The plume, silver and blue, was sideways compared to the images Harry had seen. The cloak was pinned together by a silver crescent moon upon her left shoulder, thin chains slipping into several spots across the cloak around her neck. A sheathed sword hung from one hip while a full quiver and bow hung from the opposite shoulder. She approached the Head Table and stopped a few paces away, sandaled feet clicking like leather boots. The Hall remained quiet, beyond the odd whisper.

"Presenting Helen Alexandra Potter and her attendants, Kassandra Shatter-Spear, Johanna of the Loire, Rhanis Oceaea, and her distant…cousin Phoebe." Zoë glanced back, frowning as if there was more she wished to say, but turned away at the sign of movement. Harry frowned at the last name and her description. Do I have another cousin? She can't be worse than Dudley, especially since Helen must trust her. His heart ached at the thought.

Five girls entered the Great Hall. Four surrounded a single girl, an inch or so taller than the rest. They were dressed much like Zoë, except they wore their plume-less helmets. At the center had to be Helen, who was garbed in a white dress that glowed as the clouds on the ceiling parted to reveal the moon. A tiara of silver and sapphires rested lightly upon her brow. If Harry hadn't known this was his sister, he would've wondered if the magical world hid gods and goddesses. Her hair was an auburn compared to their mother's bright red and where his skin was more pasty than pale, she was a fine olive color darkened by long hours under the sun and sky. Her gaze took in the Hall and when their eyes met, there was a split moment where he thought her eyes were the same as Malfoy's. Yet what he first thought was a slate grey was really silver. Patronus silver.

Her party stopped before the Head Table, where the teachers and visiting headmasters all sat. Zoë filed into their group, standing a couple feet before Helen. Dumbledore stood once they stopped and smiled in that grandfather nature that endeared him to Harry.

"Welcome to Hogwarts, dear Helen. We were surprised by your, shall we say, failure to arrive with your brother three years ago."

"Forgive our lady," Zoë began, but a hand tapped her shoulder and she stopped.

Helen came forward, smooth like a swan. Girls across the Hall seethed at the effortless display of grace. "If you wish for an explanation of where I have been these many years, Zoë and I can speak with you in your office. Oh, and my brother too, Headmaster. He has a right to know. More than you, frankly, but you are well known across the pond." She paused to look back at the five with her. "We have been traveling most of the past couple days and we have arrived most famished."

"I am most curious about where you have been, so I will take up your offer to speak later," Dumbledore said, acting as if she hadn't suggested anything negative of his character. "We were waiting for your arrival before we had dinner. I believe you will find someone of interest at the Gryffindor table." With that, he clapped his hands and the many golden plates covering the tables filled with food aplenty.

Harry did his best to ignore Ron as he filled his plate with a dozen different types of fried meat and vegetables. Hermione's nose twitched at the sight, but they were pulled away by a pleasant arrival.

"Hello brother," Helen said, appearing behind Harry. Some of the girls were beside her while the others stood near Hermione, eyeing the nearby boys with distrust. Their armor and weapons had morphed into the silver parkas they wore when arriving in Britain. She must have a talent for transfiguration to change them so quickly. "My sisters and I would love to join you. Well, me more than them."

Harry nodded—Sisters? He wondered. How is that? —And people shifted all down the Gryffindor table to provide the girls with a spot to sit. Most seemed nervous, but Helen was clearly enjoying herself as she sat. Now that she was close, he could there was so much of her appearance he hadn't seen. Her tiara had appeared to be plain silver beyond the grouping of sapphires upon her brow, but now he could see fine writing along the edges, all of it in what he thought was some dialect of Greek. It looked vaguely familiar with something he had spotted in Hermione's Ancient Runes book a couple weeks ago. The sapphires are going to drive me mad. They look so familiar. From Astronomy? I don't think they're also from Ancient Ruins…

"I bet you've been wondering where I've been, little brother," Helen said, filling her plate. He nodded. "You should've guessed from the little speech I gave that I live in America, not here in jolly ol' Britain. Never received a letter from Hogwarts, but Ilvermorny tried pretty hard to get me to attend their school. MACUSA doesn't enjoy the fact they have to share America with another magical, uh, government so to say, but we"—she gestured to herself and the other girls—"are under the aegis of that other government. I did consider Ilvermorny, but mother decided that since she knew the Lady of the Crossroads herself, having me attend a magic school was unnecessary."

"Why would this, uh, Lady of the Crossroads be better than a school?" Hermione asked, frowning. She leaned in. "What's her name? You can't mean—"

Helen glared at Hermione, quieting the girl. Harry was baffled, wondering, how? She turned to her brother. "Is she always this inquisitive?"

"I think she's learned some manners. She was terribly brash with her knowledge as first years." Harry glanced at Hermione and with an amused grin added, "I think she's read the entire library and we aren't even halfway through our education. You should be careful about what you say or she'll figure everything out from a few words."

Hermione flushed and those near them grinned and giggled. Helen's party smiled, more to fit in than understanding the joke.

"We have been rude," Zoë said, focused on Hermione. "I am Zoë. This is Rhanis, Phoebe, Kassandra, and Johanna." She gestured to each girl in turn, who nodded. "We…serve Helen's mother in America. Thou reminds me much of her sister and her children."

She nodded. "I'm Hermione. You all seem to know Harry and this," she said, pointing, "is Ron. Unfortunately, he has the most abhorrent table manners."

"That was clear enough," said Rhanis, her plate empty. "It's enough for even a cyclopsi to lose their appetite." The other girls nodded and Harry wondered if the one eyed monster of mythology existed in America.

We did encounter a Cerberus going after the Philosopher's Stone, so they might be real. We even put Fluffy to sleep with music, like Orpheus.

"I must ask," Kassandra began, focused on Hermione like the others. "Are you named for the Hermione, daughter of Helen of Troy?"

As Hermione began to engage the other girls, Harry turned to Helen. "They seem nice."

She grinned. "The best. I've been around them nearly my entire life. Rhanis was one of the first to join my mother and Zoë was expelled from her home by her sisters because she helped the wrong man." Helen paused, a sad look crossing her eyes. "Most of them don't have the best histories, especially with men. Mother sent them with me for protection, though they're more here to keep me company. You may get a pass from them being my brother, like how my uncle can come and go without being turned into jackalopes like mor—uh, muggle boys and men."

As their conversation shifted into more casual topics, Harry couldn't help but wonder just who this 'mother' his sister spoke of. Maybe that could explain the other girl with auburn hair and silver eyes he had seen in the Mirror of Erised.