The Once and Future King

Chapter One

'Whoso'er Pulleth Out This Sword of this Stone is Rightwise King Born of all England'

The sun rose over the perfectly normal gardens of Little Whinging, while it's perfectly normal inhabitants woke to greet the perfectly normal day that was ahead of them, oblivious that someone in their midst had been touched by the hand of destiny in a most extraordinary way.

Harriet Lily Potter, age ten, woke with a start as her aunt Petunia rapped sharply on the door to her cupboard under the stairs, her aunt's shrill voice yelling at her to wake up so she could start cooking breakfast. With a groan the ten year old slowly sat up, taking care to avoid hitting her head on the shelf above while running her hands through her messy black hair.

The pull string for the light above clicked on, and the girl took a moment to survey her domain. The cot she was seated on stretched the length of the cramped space. Underneath was an old suitcase, containing all of her clothing. On the shelf, located just over where her head was when she slept, were the rest of her worldly possessions. Green eyes stared back at her from the cracked mirror of a makeup compact her aunt had thrown out, which sat next to a small collection of old books Harriet had managed to smuggle past her relations, and beyond those were her most precious possessions in the world; a collection of pewter figurines, each about three inches tall and modeled after the Knights of the Round Table.

Harriet's inspections were interrupted again by her aunt's return, the shrieking banshee redoubling her pounding on the thin ply door. "Get Up, you good for nothing Girl!" she screeched, "Breakfast isn't going to cook itself!"

Harriet sighed at her aunt's impatience and said, "I'll be out in a minute." before pulling the suitcase out from under her cot. The raven haired girl pulled on a pair of second-hand knickers and some of the oversized clothes her cousin Dudley's had outgrown, and her relations were "gracious" enough to pass on to her. To finish off the ensemble was a wide strip of white cloth she had torn from the hem of a T-shirt that had come down to her knees, which she tied into a large bow to hold her otherwise uncontrollable hair back while leaving her bangs loose in the front to cover the faded scar shaped as a lightning-bolt on her forehead.

Out in the rest of the house was a typical morning at Number 4 Privet Drive as Harriet attended to the bacon and eggs frying on the hob, trying her best to be ignored while only paying enough attention to her unfortunate relations to know if she needed to duck her aunt's frypan or the back of her uncle's hand anytime soon. Vernon Dursley was reading the morning paper at the table, his chair faintly groaning every time he shifted his weight, and complaining about everything; Harriet's unkempt hair, The government's lack of sense, Harriet taking too long to cook breakfast, Grunnings' falling profit margin in the last quarter, and Harriet in general, just to name a few. Her aunt Petunia was doing her level best, and therefore failing utterly, to spy on the neighbors through the kitchen window without appearing to be doing so. Dudley was seated next to his father, looking much like a smaller version of the man minus the mustache while eating his third bowl of cereal, too engrossed in its sugary depths to pay attention to anything going on around him.

Soon breakfast was over, thankfully without incident, and everyone in the house went about their day. Harriet managed to slip out the door to the back garden before her aunt could hand her a list of chores and was now wandering the streets of Little Whinging. She knew where she was going, but was in no real rush to get there and had decided to simply enjoy the beautiful Saturday morning as she contemplated the dream she had had the previous night.

It had started out much like her usual nightmare of the high, cold laugh followed by the flash of blinding green light, but the end had changed. Instead of fading to darkness and her waking up in a cold sweat there had been pain, like her forehead was splitting open, and something malevolent trying to force its way in before a flare of gold washed away the green light and dark presence. A sense of protection overcame her, like she was somewhere where nothing could harm her and no evil could touch her before she drifted off into a peaceful, dreamless slumber.

With a start, she realized that her feet had already carried her to her destination. The small chapel on the edge of Little Whinging had seen better days, but still stood proudly. Father Emerson, the priest who maintained it, was sweeping the front steps. The girl couldn't help but smile as she approached, the middle aged priest steadily humming a tune to himself, lost as he was in his work.

"Good morning Father." She called, causing him to start at the noise.

"Ah! Good morning to you too, Harriet!" the priest said with a cheerful grin on his face. "And how are you this fine day?"

"Well enough..." she said, but Father Emerson seemed to notice something. Putting aside his broom he sat down on the steps he had been sweeping and patted the spot next to him.

"Come now, Harriet, what's bothering you? You know you can trust me." He said as she sat down. She knew he was telling the truth. This was the man who had taught her how to read and write before she entered primary, and had been teaching her French and Latin on and off since then. His chapel had acted as her safe haven many of the times her cousin and his gang had played at "Harry Hunting". What's more, he knew about her living in the cupboard under the stairs at Number Four, and after failing to wrest guardianship over her from her relatives had offered to let her stay at the chapel anyway if things ever got too bad. She was too young to really understand what all had been involved in his trying to become her guardian or why he had failed, but she did understand that he could get in a lot of trouble for even making the offer. The priest had been incredibly tight lipped on the subject when she had asked about it later and seemed angry at himself for something, but it was the thought that counted.

So she told him about her dream, and how it had changed. It didn't take very long, and once she was done they sat there in silence for a moment. Harriet chanced a glance at the only adult she even remotely trusted and saw that a troubled look had come over the Priest's face. Finally, he let out a sigh, nodded his head like he had come to a decision about something, and stood. "I'll be back in a moment." He said, patting her gently on the shoulder before walking into his chapel. True to his word he returned shortly, only now he had a small wooden box in hand, and the familiar tome, Le Morte d'Arthur, tucked under his arm.

"I was saving this for your birthday," he said, sitting down next to her again and handing her the box and book, "but I think I should give them to you now..."

With trembling hands she took the gifts, knowing exactly how precious the 1485 edition print was. Only two were publicly known to still be in existence, but this third copy had been kept both secret and safe by her teacher since before she was born. She didn't know how he had gotten his hands on it, she had never asked, but it was still in nearly mint condition.

And now, apparently, it was hers to keep safe. She didn't know what to think of owning the precious book, and she didn't want to think of what other people might do to get their hands on it if they found out about it.

Pushing those thoughts aside for another time, the stunned girl decided to instead focus on the box. It was beautiful; made from a rich mahogany polished to a shine, inlayed with blue enamel patterns. The catch for its lid was simple iron shaped into a lily with the "stem" curving underneath to latch it shut. Upon opening it she found that it was not empty, and without even having to get a better look at it she knew it was another figurine like the others back in her cupboard. She couldn't help but take it out for a closer examination.

Once in the light it was obvious that this particular figurine was different from the ones Harriet already had as she turned it over in her hands. The armor was expected, of course, and that its cuirass was painted with the same blue markings as were on the box was hardly coincidental. Layered silver-grey tassets hung just under the cuirass, gauntlets covered its hands and on its feet were a set of matching sabatons and greaves. The blue and gold longsword held in its right hand looked more ornamental than practical, but could still function under its original purpose.

None of these things were what caught her interest though.

First of all, the figure was wearing a dress under the armor; predominantly blue with gold trim and white petticoats underneath. Second of all, the face was oddly feminine, and the almost golden blond hair was done up into a severe bun tied with a blue painted "ribbon" with only a bit in front hanging down in an oddly similar manner to how hers was at the moment.

"Altria Pendragon, King of Knights." Father Emerson said by way of explanation from over her shoulder, earning a confused look from Harriet.

"Um... Father, isn't king Arthur supposed to be, you know... a man?" she asked.

Her companion only gave a soft chuckle as he stood up and motioned for her to follow. For some reason he suddenly looked a lot older than Harriet had ever seen him as she began following the priest around the back of the chapel. "So the Legend would lead you to believe," he said with a sigh as they entered the copse of trees behind the building, "but such details are often lost to history and fifteen hundred years is a long time to forget."

"What are you..." Harriet began, only to trail off as they entered a small glade. Light streamed through the leaves above in soft beams and the whole place was unnaturally still and quiet with an air of expectance. What had stilled her thoughts was in the middle of the clearing. Bathed in light and slightly overgrown with ivy was a squat stone "alter", for lack of a better term, that stood about a foot and a half tall, and imbedded in the middle of the block was a sword. Red enamel traced over the golden langet and crossguard in patterns that made the assembly look like a phoenix spreading its wings toward the sun. The grip was black as polished onyx, the half closer to the crossguard wrapped in suede leather that was equally as dark and indecipherable arcane script stitched its way around the division with gold thread. Set into the pommel was a pink diamond the size of a robin's egg, it's nearly blood red facets sparkling spectacularly. Traced down the gold fuller was more arcane script which ended with an engraved crescent moon while sunlight gleamed off of the silver edges.

So mesmerized by the sight was Harriet that she hadn't noticed that she was standing next to the stunning blade until she was running her finger over the inscription that ran along the underside of the crossguard.

"Whoso'er Pulleth Out This Sword of this Stone - is Rightwise Sovereign Ruler Born of all England" she whispered with no small bit of wonder. It couldn't be real, her brain was telling her. All the stories said that Caliburn, the sword that chose the king, had been broken and the pieces lost. Also, if this was supposed to be the same sword then the inscription was wrong. It had to be one of the father's pranks, she told herself. 'Yeah,' she thought, 'the stories are just that; stories...'

It was a depressing thought, but Harriet already knew that life was full of disappointments.

"It's not." came the voice of Father Emerson from over her shoulder, causing her to start in surprise. She had completely forgotten that he was there.

"It's not what?" Harriet asked after regaining her composure, now tracing her finger over the intricate carvings down the fuller. Even if it wasn't "real" it was still a beautiful sword.

"Caliburn." He said by way of explanation as he lightly placed his right hand on the crossguard. "Not anymore anyway. As it stands this sword currently doesn't have a name as its legend has yet to be born..." This statement earned him Harriet's full attention.

"The world would have everyone believe that Caliburn was lost after it was broken, but... Merlin, collected the pieces and remade the blade in preparation for when Altria would be born again. She is the 'Once and Future King', after all." The priest finished, moving his hand up to the grip and giving it a good yank. It didn't budge in the slightest.

"Surely you can't be serious." She said, with a chuckle, still thinking this was one of the practical jokes the Priest was so fond of. The laughter died quickly at the grave look he was giving her.

"I- It can't be real, can it?" she asked with no small amount of hesitation. "You can't mean that I-"

Harriet cut herself off there. It was all too surreal. Everything about everything she knew was telling her that none of this could be real. King Arthur and Camelot were only myths along with Merlin. Magic didn't exist, as her relatives made a point of frequently reminding her despite all of the strange things that happened around her. Running from Dudley's gang at speeds that could outstrip an auto was her imagination running away from her. Leaping over one hundred feet from the ground to the top of her school's chimney and then safely back to the ground before anyone saw her was the wind catching her in the right way. The door to her cupboard ripping clean off its hinges from a slight push when she was locked inside and had been forced to miss every meal for a day because her hair had grown back from a hideous bowl cut her aunt forced on her was simply dry rot.

But...

But what if it was real, the rebellious part of her brain asked her, what if her relatives were wrong and Magic, Heros, and Kings of legend were more than simple myth? What if the strange things that happened to and around her were signs that she was in fact a part of something greater than she could have ever imagined? What if her relatives' explosive reactions to the incidents they found out about were borne from fear and denial rather than simply taking things out of proportion?

Her gaze drifted back to the sword imbedded in the stone alter in front of her. Hesitantly, not daring to believe that it could be true yet being unable to tear herself away from the possibility of "what if?", her hand reached up to the hilt of the sword.

As her fingers curled around the blackened leather Harriet was momentarily halted as Father Emerson gently grabbed her wrist.

"Harriet," he said from her right as she was still unable to tear her eyes away from the sword in front of her, "should you be able to pull it from the stone, you won't be the same. You will be a ruler. Perhaps not in title or deed, not yet anyway... Concept shall be your realm and ideal your duty What these concepts and ideals shall be are yours and yours alone to decide. If and when others find out they will no doubt attempt to influence what these will be, but to be a ruler by its very nature is to be alone, standing above all others even among those who are closest to you...

"The decisions will be yours, and the consequences that come with them will be your burden to bear, so be absolutely certain about what you are about to do..." His piece said and wisdom imparted the priest lifted his hand and backed away leaving Harriet with her fingers loosely wrapped around the hilt.

Minutes passed in silence as Harriet thought about everything that had happened to her; Her mistreatment at the Dursley's, the kindness she found in the presence of Father Emerson's chapel despite his love for the occasional practical joke, the stories she had read and that had been read to her by the priest and the lessons they imparted.

She thought of everything she hoped to achieve in life. Being ten Harriet had never thought about such things in any real detail before, but put forth the effort because she knew that her decision here would alter the course of her life until the day she died. This was no knights' tale from a book, no noble figure from a legend passed down through the ages. This was happening to her, here and now...

'Honor. Chivalry. Justice. Equality. Peace.' She thought, decision made and resolve firm, 'Honor shall be my armour, and Chivalry my shield. Justice shall be my blade. Equality and Peace shall be my aspirations.'

With those thoughts in mind her grip on the unnamed blade's hilt tightened and she began to pull upwards. At first it didn't move and Harriet was beginning to doubt that it would, but then it happened. A slight tremble in the stone's grip on the blade was accompanied by a quiet "tink". The tremble became a hairsbreadth, which became an inch. Slowly but surely an inch turned into foot and with a rasping ring the block relinquished its grip on the blade.

Harriet could hardly believe it as she held the sword aloft. It was heavy, requiring both of her hands to hold it upright now that it was free. She could almost feel it humming in contentment in her grip as though recognizing its true master before its entire length from tip to pommel glowed a soft white that seemed to encompass all the colors of the rainbow before shrinking down to a size and weight that was more manageable for her. Somehow she knew that it would grow as she grew, and so long as she stayed true to the ideals she had declared herself towards when she pulled it from its former resting place it would never fail her.

A hand was placed on her shoulder, and she turned to look into the melancholic face of Father Emerson. In a way he looked sad even though what he said next was spoken in a tone of respect.

"Long live the king..."

End Chapter 1

And now for some Extra Scenes!

Chess (First Year before Yule Break):

Harriet studied the board in front of her with mild interest as the redhead across from her scowled at the pieces. She had finally been roped into playing him after Hermione had lost spectacularly and now everyone in the Gryffindor Common Room was watching with rapt attention at the longest running game against Mr. Weasley seen to date. Her shrunken and animated figurine of Altria stood stoically among her knights, Excalibur held with both hands point down as she "surveyed" her battlefield. Sir Gawain, who had been playing a rook, had been lost in the previous turn and stood at the side of the board with the Sirs Ector and Kay along with a number of pawns represented as faceless soldiers. The Twins had given up their joking commentary an hour ago as the game became progressively more serious.

"Lancelot to E-Six" she said. The piece gave her a salute and moved two over and one up to comply with her order.

"Check."

Everyone in the Common room went absolutely still at the declaration even as Ron's scowl deepened. It was probably the first time anyone had ever seen him put into the position. Minutes passed as the youngest Weasley male examined every inch of the board, Harriet's face perfectly impassive all the while so as to give nothing away, before giving a resigned sigh.

"Checkmate." He said with a grimace. The room erupted into applause and quiet cheering as they stood from the board. Ron gave her a nod of respect as they shook hands over her victory.

"Play again some time?" he asked as she shouldered her bag.

"Sure!" Harriet said with an easy smile, "I guess you'll do until I go back home and get to play Father Emerson again. I need to keep my skills sharp if I ever want to beat him after all."

Ron looked intrigued even though he nodded his acceptance of the future challenge. Turning through the crowd she soon caught sight of a familiar head of bushy hair and rushed over to her smiling best friend before dragging her towards the Portrait Hole.

"C'mon Hermione! Let's get to the Library. I want to finish my Transfiguration Essay before Lunch!"

The chamber of Secrets:

"Speak to me, Slytherin, greatest of the Hogwarts four!"

Harriet was already in motion as the mouth on the giant bust of Salazar Slytherin opened, grabbing Ginny's prone form and moving it behind one of the pillars and out of the way faster than a normal human, whether they be mundane, wizard or mage, could hope to match.

Wind blew wildly around her as she released Invisible Air, revealing Coraburn in all its gleaming glory as she rushed back to the middle of the chamber. Prana flooded her circuits and she traced her blackened armor over her Hogwarts robe with the addition of a visor like helmet forming to shield her eyes completely. "A true Swordsman need not be able to see their opponent in order to strike." She remembered her first teacher saying to her while her eyes had been bound by a blindfold, "Sight alone can be deceiving. Sound, the vibrations felt through the ground and occasionally even smell can tell you just as much if not more than your eyes ever will about the foes you will face."

Thus reminded she focused on her other senses. The thudding splash of a heavy body striking the pool beneath the statue was all she needed to know that the basilisk had made its appearance.

'Damn, that thing must be at least sixty feet long.' She thought as she heard it slithering across the floor.

"Kill her, but leave the other for now!" she heard Riddle instruct the beast in Parseltongue.

The angry hiss was all that warned Harriet of the incoming strike and in that moment she had drawn on her inner strength and leapt back over twenty yards. Coraburn hummed in her gauntleted grip as she fed Prana into the blade and with an incoherent yell and downward slash she released the pent up energy. The rushing sound of what she knew without looking to be a prismatic slash of holy light soared away from her sword, ripping up the stone floor of the chamber before striking its intended target.

The basilisk gave out an angry shriek of pain, spitting poison that hissed as it struck the floor where she had been only a moment before. She knew the first strike wouldn't be able do much damage, especially from that range. The giant snake's thick, magic resistant hide would make sure of that. Feeding Prana into her sword once more, Harriet held off on releasing it even as she rushed forwards.

"What are you doing you fool! Kill her! KILL HER!" the shade of Riddle hissed.

It wouldn't do any good though. She was already parallel to the beast's side. Sword met scaly hide and Coraburn's magically enhanced edge bit deeply into the basilisk's flesh, electing another angry hiss and a lightning fast strike of its fangs to where she had been half a second before. But Harriet was already gone, now running down its length and cutting a bloody furrow in her path.

'It's time!' Harriet thought as she felt the energy contained in her sword peak. Its radiance would be absolutely blinding had she been able to see it.

The snake had slowed due to its injuries and was now hissing and spitting in pain and anger, lashing out at her in a futile attempt to fulfill the task given to it. With a mighty leap she jumped over its head faster than the eye could see, just barely missing its fangs once again.

"Cora-" she yelled as she twisted in the air. Riddle was now hissing and spitting that she was above, but the Basilisk was still confused from her sudden disappearance.

"BURN!"

Prana poured from her sword as she stabbed it straight into the top of the basilisk's skull, releasing the entire payload into its brain and blasting out the other side in a spray of black blood and venom. The entire length of the snake tensed for only a moment before crashing back to the ground even as Harriet yanked Coraburn free and leapt off and away.

'That took a lot more out of me than I thought it would.' She thought as her feet touched the ground again. Her body ached all over and she was breathing heavily as her armor faded away into motes of scattering light. Coraburn served as an impromptu crutch for the moment it took her to recover enough to stand on her own power and she looked toward where the shade of Tom Riddle stood, anger at his servant's demise writ clearly across his face.

"You may have killed the basilisk, but in a few moments Ginny will be dead, and then nothing will stop me from killing you once and for all..." he said, raising Harriet's discarded wand in her direction.

She couldn't help it as she burst out laughing at the ridiculousness of the claim, her physical fatigue and mental exhaustion factoring in to wear her self control enough to let it escape. The thought that he, a normal human, albeit still possessing the powers of a Wizard, could hope to match her, the reincarnation of the Heroic Spirit: Altria Pendragon, was so absurd as to render her into peals of incoherent laughter that echoed off the stone walls of the chamber.

Sure, he might get lucky. If he was fast enough on the onset and fired a spell before she reacted he might be able to kill her, but should she delve into her Heroic Spirit aspect again Harriet could cross the distance between them before he could finish uttering a single syllable and separate his head from his shoulders with a single swing of Coraburn. She would pay for it later, as her physical body wasn't used to the strain yet and she had already drawn heavily on her Heroic aspect when she had fought the basilisk, but the outcome of such an encounter was almost a foregone conclusion.

That would never happen though. She wouldn't let things get that far.

Forcing herself to calm down, though still chuckling, she almost lost her composure again at the furious look on Riddle's face as she slowly walked towards the diary that lay forgotten in the middle of the chamber. Her Mage Circuits came to life one more time as she once again fed Prana into her sword.

"What are you doing?" the shade asked, fear tinting his voice as he moved himself between her and the book.

Harriet simply brushed him aside, causing him to fall in a sprawled heap on the cold stone. Her wand skittered against the flagstones as he let it go, but Harriet paid it no mind as she raised Coraburn's hilt over her head with both hands. She could sense the darkness within the pages of the book, and knew that it formed a link between Ginevra Weasley and the nearly corporeal shade behind her. So long as it existed Ginny's life would be in danger even if she found a way to temporarily reverse the transfer of life energy between them.

It needed to be destroyed.

With a downward thrust the magically augmented tip of her blade pierced the cursed book from cover to cover and proceeded a foot into the stone floor below. The holy energies contained in the sword were too much for the diary's protections to safeguard against and the pages began to burn around the "wound" even as ink poured from it in a sick parody of blood. Riddle's wailing shriek of "No!" was nearly lost over the diary's own wailing.

In a moment it was all over. Looking over her shoulder Harriet made sure that the shade had disappeared as well before giving a sigh of relief, collapsing on her bum and finally letting the exhaustion and pain begin to settle in. She knew she wasn't done yet, but resting a moment wouldn't hurt too much.

Minutes passed in silence before a cough from behind the pillar where she had hidden Ginny roused Harriet. Concentrating for only a moment as she stood she wrapped Coraburn with Invisible Air once more, rendering it invisible to the naked eye before rushing over to her young friend.

"Ginny, are you alright?!"

Comments:

Quite a bit longer than the single scenes from before, but this one just wouldn't. Leave. Me. Alone!

The reason I'm not carrying it out into a full blown story is because I honestly don't think I know enough about the background and mechanics of Magic, Heroic Spirits, Divine Beasts and so-on in Nasuverse to be able to both do the story justice and do so without screwing something up along the way...

This little iteration was actually inspired by the Excalibur Challenge set by James D. Fawkes where Harry somehow gets his hands on Excalibur with one of the options being that Excalibur is the one from Fate/Stay Night, combined with me having just finished reading Fate/Revenant Sword by said author.

Of course, I took this a step further and made "Harriet" the reincarnation of the Heroic Spirit: Altria Pendragon, so it doesn't quite qualify, but that's just semantics at this point. She also wouldn't get her hands on Excalibur until well after graduating Hogwarts, if ever, so that would also probably disqualify it from the challenge criteria, but... meh...

There were also a few more "Extra" scenes that I was considering writing, but decided to cut things off here...

Plot (for those who are interested):

This one would start out with Chapter 1 as seen above, which takes place about two weeks before Dudley's 11th birthday, and would somewhat follow Harry Potter Canon with appropriate alterations given the changes. Father Emerson may seem like an OC, but in this case that's only partly true as he's actually Merlin (Aka: Myrddin Emrys) survived to the present day. To this day he's been hiding from the Wizarding world, Mages Association and the Church, both so as not to be bothered by them and as to allow himself to be there when the reborn Altria should make her appearance.

The idea is that Wizards and the Mages Association were at one time one in the same, but a little before the founding of Hogwarts the two split over their ideals and ideas on how magic should be practiced. The Mages simply wanted to uncover the mysteries through science and study, utilizing their powers trough their magic circuits. Wizards believed that Magic was only possible through "bloodline", and utilized their blood as a means for channeling their Od into Prana instead. Over time the two groups steadily drifted apart, eventually becoming hostile towards eachother for reasons lost to history until the Statute of Secrecy had the wizards going into hiding from the whole world, including the Magus cousins. The Mages Association knows they exist and has a general idea of how to find them, but don't bother with it unless a Wizard does something completely outrageous, a line Grindelwald and Voldemort came very close to crossing in the recent century.

After she Pulls Coraburn from the stone Emerson explains to her about Magic, both Wizarding and the Mages Association variants, and begins to instruct her on building her Mage Circuits while teaching her the basics of Thaumaturgy. Later, and especially during the summer before her Second Year at Hogwarts he begins teaching her Projection/Tracing so that she can summon Armor to herself whenever she needs it. I imagine the design she eventually comes up with as something like a "Black Saber Lily" (hence the white Ribbon in her hair at the beginning).

The enchantments on Coraburn are similar to those on Caliburn, though instead of stopping her aging process right away it waits until she ages to maturity, and the runes circling the grip are a spell that prevents her from being forcefully disarmed. Its redesign from its base as the actual re-forged pieces of Caliburn gives it all the "Weight" of its predecessor's legend, meaning that a projection or Fake of Caliburn won't defeat it in that manner even though Garm, Merodach and the other predecessors still will. As for the physical design, it was taken mostly from my own imagination of what a remade Caliburn might look like mixed a bit with the description of Anduril (Aragorn's Sword from LotR), seeing as it's also a re-forged sword of a King.

Harriet also has to deal with being the reincarnated Heroic Spirit of Altria, rather than just the reincarnation of the King of Knight's mortal soul. I'm honestly not really sure how this would work, but I think it would have something to do with the end of the Fifth Holy Grail war in about ten years. What it basically means is that even though she has a mortal body she can temporarily tap into the powers granted to her because her soul is that of a Heroic Spirit, essentially making her a God among Mortals for however long she can hold it. The drawback is that her body is still that of a mortal, and if she taps too much into that aspect for too long she will begin to destroy herself until her body becomes acclimatized to that level of power. Over time she will be able to hold it for longer periods, until just before the beginning of the Fifth Grail War when she will be able to maintain it nearly indefinitely.

This also means that because Saber took Avalon with her at the end of said Grail War it is now grafted to Harriet in a similar manner to Shiro as it was reincarnated with her, though she maintains most of the full benefits (Sans the not aging, at least until she hits maturity) at all times because it responds to her Prana. This is the only reason she is able to survive tapping into her Heroic aspect for even a moment in the beginning, as otherwise that much power would have ripped her physical body apart. She learns about it with Emerson's help before Fourth Year and would use it in the graveyard to block Voldemort's Avada Kadavra. It's also what protected her form the same spell when she was one and prevented the Soul Fragment from latching onto her altogether, as nothing corrupted can enter paradise.

After the end of the Second Blood War she would go on a bit of a "Round the World" vacation that will last a few years, with her ending up in Fuyuki around the start of the Fifth Grail War. She would go on to assist Shiro, Rin and Saber throughout the conflict, and where the story would go after that is anyone's guess...