(da Vinci's Workshop)
da Vinci skated about her workshop employing her toolkit of various analysis Mystic Codes, most of which looked like lenses, magnifying glasses, telescopes and so on. Unsurprisingly, nothing came up that contradicted the Control Room's initial in-pipe readings. It went without saying that the Rulers stayed nearby, though Martha and Georgios had to occasionally move to the corridor outside to avoid disrupting some of the more delicate measurements.
"By the way," da Vinci said suddenly. "Is that Kaleidostick a separate person? They're not in your True Name like with a pair Servant such as Anne and Mary."
"Hmm... under the Personal Skills section," the one being asked responded after taking a moment to check. "Though the documentation is terrible; what does 'apply random effects' even mean? I don't know myself."
"That's clearly because I'm not an ordinary Mystic Code," the shady Kaleidostick spoke up cheerfully. "Oh and if you were wondering, being a magical girl is under Class Skills along with your Realm Creation and the like."
"Right." da Vinci put away her various instruments, some into drawers or on shelves, and a select few into her backpack. "While that bit makes sense, I suppose, it's a bit odd that you've somehow lost height (and weight) despite supposedly not having variants; changing class container shouldn't have that much of an effect."
"Aren't these statistics rather fuzzy anyway?" Sasaku frowned despite her apparently uncaring tone. "I mean, looking at you..."
"I already explained that, didn't I?" While they would have been nominally the same height, da Vinci's roller skate-modeled Mystic Code made her slightly taller. "Creative-types sometimes get recorded while young. Or maybe when they get Heroic Spirit status the Throne just goes back and grabs a younger copy, same outcome, really."
"Yes, but I'm pretty sure no one in Italy when you were there was wearing a sailor uniform. And while there are plenty of variants in Japan, none of them use slashing like on those sleeves," Sasaku retorted. "Also, why the backpack when Servants have Inventories anyway? I didn't see Kojirou carrying his massive sword around when it wasn't needed at hand."
da Vinci seemed upset over the evaluation. "I'm an artist; I designed it myself. Besides no one told me your friends set up the Fuyuki Holy Grail all the way over in Europe. Between your (Realm's Armory) and Gilgamesh's (Gate of Babylon) you might not have realized that a non-Skill Inventory has quite a lot of limitations."
"Don't take it to heart," Ruby interjected after placing itself at a safe distance away from its contractor. "She's just upset at being stuck with a conventional uniform. But don't worry, leave it to me to ensure your magical girl transformation is mind-blowing. Fufufu~"
"Huh?" da Vinci's eyes tracked the magical stick as it flitted about. "But she looks exactly like in the picture-"
"What picture?" the subject immediately asked. "Wait, don't tell me..."
Opening the folder which she had been referring to, da Vinci fished out what looked like a photograph from an instant camera and handed it over without comment. Sasaku took one look it at and exploded; or rather, Ruby was flung halfway across the room in a sudden shower of sparks. "This was your fault?!"
Despite the awkward angle of the shot, she could easily identify the taker as being Ruby held by Kuro just before the latter tricked her into forming a contract with the Kaleidostick. "No wonder all those homunculi could recognize me on sight; what other Servant would show up wearing a Homurahara. Sailor. Uniform."
At that moment, Ruby was discovering that, perhaps as a side-effect of being a Skill, it wasn't harmed by Sasaku's impromptu attempt to test its durability. "Actually... quite a few, so you're in good company."
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(Gudako)
While her fellow Master was doing the rounds, she had been watching everything unfold in the da Vinci's Workshop. It seems like there's no real cause for concern. For one, Artoria's results had come back with significant amounts of Grail mud corruption, but the person herself seemed quite fine. Meanwhile the pseudo-Grails they had been encountering didn't seem to be tainted at all, and were much weaker than what Chaldea had projected for the Greater Grail's capacity.
She turned to Jeanne. "Could you get 'hime for me? Bring her to My Room." The Ruler seemed to disapprove of dealing with the Berserker, but went without complaint, tagging in Martha from the corridor on her way out.
"It's time we wrapped up here," Gudako announced, interrupting the rather inconsequential discussion taking place. "da Vinci, I'll leave you to run the follow-up analysis, message us if something comes up."
"Sure." Reclaiming the photograph for her folder, da Vinci waved everyone out of the workshop.
The group of four made their way towards the residential area without incident. However, they had to travel some distance because Chaldea's layout placed the apartments near the bottom of the complex, and the planned elevator system had not finished construction by the time that the Separation Order was enacted. Still, it was a good call to fill up to personnel capacity even though we didn't have everything fully set up.
The Master did not miss the fact that they passed by a few of the human magi, but not any of Chaldea's far more numerous homunculi. No pressure, right? It was the same reason that this particular task fell to her rather than her fellow Master or both of them together, unlike their Rayshift deployment order.
"We're here," she said to the one member who couldn't identify the pair of unmarked doors they were standing in front of. Gudako walked up and tapped her fingertips against the featureless surface, which slid open obediently to reveal a spacious room that did double duty as bedroom and office. Glancing around out of habit more than anything else, she made her way over a low table surrounded by several colorful cushions and sat down.
Nodding towards the space available, Gudako picked up the folder she had left on the table as the door, which had closed automatically after everyone had entered, opened again to show Jeanne holding firmly onto the arm of a younger girl. The latter, as predicted, tried to dart inside but couldn't get free of the Ruler.
"It's alright," the Master sighed as the horned Servant, when released, immediately made a beeline for her, only to have Martha get in her way. Turning her attention to Sasaku, she asked, "Do you happen to know who she is?"
The two Servants looked at one another with interest for a moment, but not much longer. "No."
After blinking in surprise, Gudako passed the folder over. "Don't Rulers get (True Name Discernment)?"
"Sure. A low rank one that is more like being able to search a database." Sasaku flipped open the folder, read the top of the first page, and glanced back at the other Servant, whose focus had returned to their Master. "I'm seeing some sort of pattern here. You must be the twelve-year old variant of Kiyohime. "
"That's right," was the simple dismissive reply.
Nodding, Sasaku turned away from Kiyohime. "So did you or da Vinci write the red font warnings?"
"Neither. Gudao did, since she latched onto him first back in the Wyvern War Singularity. That about right Kiyohime?"
"Yes~"
Taking back the folder, since it clearly wasn't necessary, Gudako switched to business. "Let's get to the point. It's currently 20th October 2019, closing in on three months since the beginning of what we're calling the Incineration of Human History. As far as we can tell, besides the Singularities, there's simply nothing past the boundary of Chaldea's Realm, which I'm sure you recognize the foundation of." This received a simple nod in acknowledgment.
"I can guess, but about the Four Houses that Martha here mentioned...?"
The Saint looked surprised at this. "How can you not know, I thought you started that?"
Gudako shook her head, catching the Servant's attention. "Though there isn't documentation of it, Our Lady here created what we refer to as the Triple Alliance, or Triangle Alliance for obvious reasons. That era lasted for about two years from the end of the Fifth Fuyuki Holy Grail War. Although the Four Houses were created about a year before the Founding Conflict, it was our first major action, so either one may be referred to as the Founding today."
She looked apologetic for a moment, before continuing. "As you probably guessed, the Four Houses are Emiya-Matou-Einzbern-Tohsaka. There are also several other individuals, organizations, or families with observer status." Gudako took a short breath. "Now regarding the Founding Conflict, I wasn't around then but..."
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(Second Meeting of the Four Houses, Einzbern Castle, Fuyuki, 2008)
"We are agreed then." Shirou paused to give space to the light clapping of the homunculi around the room. Illya for her part only looked thoughtful, or perhaps that was just due to the faint lines making the effects of Sakura's Imaginary Space evident.
"Quite a lot will depend on the Einzbern not having moved their workshops or observatories in the last three years," Rin tapped the table nervously. "Granted, the leylines in those places are important strategic objectives anyway."
"We're quite well-equipped as is, I'd say," Sakura tried to reassure her. "How many Jeweled Swords do we have at the moment?"
"Just two of the new five-ply ones, besides the three-er," the red magus replied with a lack of enthusiasm for the achievement that her previous self from a mere three years ago would have found miraculous. "If we hadn't lost Caster, she'd have unlocked this thing's secrets by now." Rin waved the Sword she had on her person for emphasis. Its younger sibling was still in the workshop for evaluations.
"I'll take the second," Shirou immediately added. "Sakura, you should be fine holding the rear with the prototype one."
"Wait a moment-" his wife started, at the same time as Illya argued, "I didn't ask you to do the fighting for me."
But he overruled their objections. "Illya, you will literally die if you try using one of the Swords in your current condition. And I'm already getting bad feelings about leaving the kids behind, so it would be really helpful if you and the others could hold down the fort. Er, castle."
"Besides," Saber spoke up dryly, "The last time I went to battle alongside little girls, they all died."
"That was uncalled for," Sakura was a lot less hesitant to speak her mind after the group's years working together. "But yes, our best approach is to put as much as we can on the offensive and stay mobile. Also, if the two of us have to be separated, it's best for Illya to stay here in the Realm rather than be out in the open."
"It doesn't sit well with me to be hiding out in Fuyuki to avoid running out my lifespan timer while my little brother is out on the front," the homunculus grumbled, but she nevertheless conceded for the sake of her niece and nephew. "Just don't take too long or your children will be heartbroken."
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"Hold that bit," Sasaku interrupted her Master. "We all died? So then Chloe..."
"She was already the Fuyuki Singularity's Archer when we got there," Gudako explained. "We summoned her only after the following attack, so she had about two months over you."
"And the humans were caught in that Incineration of Human History?" Sasaku frowned when Gudako hesitated, which was practically an answer in itself.
"The three of them, and my mother, were in Chaldea. Though we only found two of them after the attack, it's certain that they're all dead." The answer was delivered flatly.
Everyone froze for several seconds before Sasaku, running a hand through her faded red hair, muttered into the air, "That can't just be a coincidence."
"Certainly not," Georgio said evenly after it was clear no one else wanted to answer. "It happened after the Separation Order was enacted, and only the presence of Tohsaka would have been known to an outsider. Well, the other three were in the same place, but by themselves so they were clearly targeted unlike all the other casualties."
The smaller Ruler didn't respond except to idly wave her hand at the air. "And the children?" she eventually ventured in a low voice.
"They are here, very much alive and quite cute," Jeanne said with a bit of cheer returning into the conversation. "You haven't met them yet, but they're probably already waiting for that. There's also the two Masters who you've alrea-"
"Mhm." By very quietly, but perfectly audibly to Servants, clearing her throat, Gudako stepped back in. "I was about to get to that." She simply pointed to her orange-red hair, which would have been remarkable on its own. "The Founder, Illyasviel von Einzbern, is my mother. And my father was your student... but you don't seem surprised by that."
"He did get involved in a magus family war when she asked," Sasaku shrugged. "But judging by your fellows, most are still produced like your mother's maids?"
"Unfortunately, that is still the case. Early on, we tried to replicate my mother's birth, but were forced to shelve the experiments for later. While the Einzbern methodology is certainly the pinnacle of homunculus production, it nevertheless has various fundamental limitations. For one, the World seems to heavily dislike the potential for us to reproduce in the usual way."
Gudako shrugged though the next part is probably the critical revelation. "However, as my father's wife pointed out to my mother, if we have the means to produce homunculi, and the means to produce those means, there's no issue as long as there isn't some other constraint, say, on our total numbers. Which may exist, but we haven't reached it yet."
The Servant facing her seemed unsurprised by this. "Before all this went down, how many of you were there?" She wasn't asking about Chaldea.
"When we were making the list of who would be transferred to Chaldea, there were approximately ten thousand of us between Japan, North America and Germany."
"Mhm. When I told Sakura this might happen, I didn't think she would take it as a prophecy to be fulfilled. In fourteen years... it sounds like the Four Houses was pretty much the Einzbern and a few hangers-on even before."
"Never!" Hotly disputing the possibility despite feeling a building pressure that belied the sedate exchange, Gudako said the first thing that came to mind. "That would contravene the covenant cut by our predecessors. Aren't you looking down on us a bit too much for not being humans?!"
The other Servants, sensing that something had gone wrong, moved to intervene - Kiyohime probably being the fastest to whip out her fan - but Sasaku simply sat frozen in place, thunderstruck.
"No weapons in My Room." Gudako said firmly. "I don't see you fanning yourself with that, Kiyohime. Holy Knuckles too, Martha."
"Who told you that covenants are cut rather than signed, made or covenanted?"
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(Fifth Meeting of the Four Houses, Einzbern Castle, Fuyuki, 2014)
Although they had seen it several times by now, the two homunculi couldn't get used to watching someone's shadow spread out across the stone floor like a thick viscous mud.
"Stand back," Sakura said while standing perfectly firmly in the middle of the liquid shadow. Stepping down into it, she carefully lifted Illyasviel out of the darkness much like a mother would a sleeping child. The shadow, its purpose complete, rapidly rolled back into itself beneath her, disappearing without trace in the surrounding light. Opening her eyes as Sakura let her down onto her own feet, the Founder of the (new) Einzbern order and murmured thanks before turning her gaze towards her two descendants.
"There's half an hour before the meeting." With that, Sakura left to give the three some privacy.
Illya looked down at her arms as a chair flew itself over for her to sit on, frowning at what looked like several black gashes eating into her flesh. "Nine years ago, we thought this body would not last two years. Even with stasis-like protection, Sakura's magecraft is simply too corrosive; one thing or another will do me in before too long."
She motioned for them to sit. "I hope you've been getting along well with your father's children. They should be about seven now, right?"
"Yes." Siegfried hesitated before adding, "Iri and Matthew say hello."
Illya chuckled wistfully. "They're too young to know me. Anyway, you're five now, short for humans to become adults but long for us. While you'll be joining me in the Four Houses' collective covenant, there are some things which I am about to tell you that must remain an Einzbern secret; you pass it down to your children after you, but not to anyone else."
She paused to gather her thoughts before continuing. "This isn't part of the Houses' sharing agreements, in part because it is not a magecraft or generally known even within the Einzbern. One of you, or perhaps those following you, will hopefully encounter if not summon the Caster Sasaku; I needn't remind you how much we've been making use of her Realm magecraft since getting it from the Emiya House. There are a few very specific things you need to remember to say to her when you make contact..."
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"It was my mother," Gudako said simply.
Satisfied, Sasaku nodded, usual calm restored. "Your actions and your zeal commend you greatly above many peoples; to have held to the agreement between your mother and me is laudable. But tell me - you hardly asked me anything, did you ask for Kiyohime's presence as a second witness?"
The homunculus grinned, the answer clear. "Your fellow Rulers might not have noticed, but by now you must have gained admin privileges to the System, even if you didn't have it in hand right on being summoned." Kiyohime was about to take the chance to latch onto her, but Martha intervened, much to the other Servant's annoyance.
"Wait a moment!" Jeanne seemed alarmed by this. "You mean Chaldea's System!?"
"You saw da Vinci's readings, that was the original (Realm Creation) Skill. Unless it's a specific magecraft, we use a devolved version of the Authority that functions within the Realm. Though it seems to have dropped from her True Name at some point, the current Emiya magecraft is from her. Emiya Kiritsugu did not pass his crest down to anyone."
"You kept this massive liability from us?" Georgios was not as amused by this. "If she had overturned the Separation Order we'd all have died instantly."
"That would be very unlikely, since the system fundamentally won't allow such an obvious single point of failure. Also, you're still obsessing over what a Berserker did in Italy."
"I get the sense you're all expecting me to know about that. But I don't, so you know." Sasaku reminded her. "And to be clear, what just happened is you giving me that administrator access."
"What's another surprise added to everything today?" Gudako sighed and motioned to Georgios. "Can one of you fill her in on the Roman Singularity? da Vinci is going to be seriously annoyed when she realizes how the Grand Aria system works thanks to this."
Jeanne looked skeptical when the Master made clear her intent to leave matters at that. "You just said something rather ominous, don't you think? Besides, I thought da Vinci designed the Grand Aria system."
"No. It existed before she was summoned, even if it wasn't named then; because that is precisely the system which enabled us to bootstrap a Holy Grail and a mass of Tohsaka's fancy Saint Quartz to summon a Servant before the current Grail War started. You can say that da Vinci designed the instrumentation, like what's in the Control Room, but fundamentally the Grand Aria is something within us." Gudako pressed a hand to her shoulder.
"Even the finely crafted runic magic circle-like circuits etched into the structure of Chaldea wouldn't be able to maintain the Realm's integrity against the void outside left by the Incineration. If you wondered why the the Grand Aria isn't sung anywhere, that's because it's maintained by a unified act of will. In many ways, the collective will of us homunculi is also the will of the homunculi collective. The system is everyone and no one; it only exists on a meta-level and assents to guidance but isn't bound."
Nodding, Sasaku asked, "So what just happened is..."
"We were all waiting for someone to provide evidence to make a decision. This time, that someone was me. Though the Grail seems to allow multiple Rulers, it only wants one to be filling the role left unfilled by an Overseer; it's no mistake that you were the one with Command Seals rather than, say Martha as previously - this was precisely what we were looking for."
"Huh?" Apparently, something in that had caught Kiyohime's attention. "She has Command Spells?"
"Mhm." Gudako gave her newest Servant an apologetic look. "I guess she, too, is an Anchin."
"Wait a moment!" Sasaku immediately recalled some of the Grail's information on Kiyohime's particular obsession. But it was already too late.
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Additional info:
Realm Creation is a variant of the Caster class' standard skill, Territory Creation.