Wine, Chickens, and Magical Studies

Shiki sat in a chair nearby and scanned the books on the shelf.

Touko leaned back against the table. "I heard a little about the Holy Grail War. Seems interesting. A way to reach the Root using Heroic Spirits, right? Have to say that's a rather novel method."

"Hyphen? Married into the family, huh?" Hideto sat on one end of the sofa, looking around curiously. The magic was vibrating around him, like being at a rock concert in his youth and feeling the speakers boom into his bones. Was it... Wrong to say he missed it?

"Oh, please, I don't want to cause trouble. You've already done a lot for me and mine, it sounds like. I'd like to thank you and your wife properly for taking care of my bro-brother and my daughter." Hopefully the sentiment would cover up the weird choice of words? He didn't remember the Tosaka having a daughter, either, but - wait, there was something the old man mentioned, wasn't there? Oh! OH! Oh. Uh, at least he didn't put his foot in his mouth... sheesh...

A humming voice familiar to him echoed from upstairs, and he brightened as soon as Mari came into view. "Mari! Papa made it!" He laughed as the girl turned on one heel and made to go back up the stairs.
--
In the library, Phillipus leaned in a less dignified manner against the wall. "I suppose. I have to admit, I don't know a lot about the original families' plans, or how exactly the summoning works, but here I am. It's a means to an end, at any rate - if one must charge a vessel with spirits, why not make it as grand as possible?" He smirked.

"Oh it's no trouble at all!" Lazarus assured. "And yes, I did marry in-Oh! Mari please don't go! I'm sure your father wants to speak with you!" While he waited for her to approach, he motioned towards Ayaka, "This is Ayaka, by the way. I'm sure Mari told you about her."

Ayaka started and waved shyly. "Ah... um... hello. You must be... Byakuya's brother? Pardon me for asking."

*****

Touko slumped down into a seat and flipped open the silver case, revealing the prosthetic inside. "I see, I see. I must admit I'm a little curious to see the outcome, but... Well, trying to reach the Root usually doesn't end well. Seems like you've got a good setup here, though. Good luck with it."

Hideto grinned. "The younger and more charming brother!" Mari lightly whacked his shoulder and spoke up. "That's the way he is. See what you gotta get used to?" He shrugged.

"At least I'm not boring, right?" She sighed and sat next to him before flashing Ayaka a smile.

"He's a nerd, but he's a good dad. You'll be in good hands."
--
Phillipus chuckled. "Much appreciated. It's a lot more complicated than the War we're meant to be involved in, but... Well. We'll see how it goes." He winked before taking his leave.

Lazarus chuckled, "I definitely can't argue with the 'more charming' part. But Byakuya was a victim of circumstance. Oh! I forgot the coffee!" he rushed into the kitchen. He'd also forgotten that he'd stopped halfway through making himself a sandwich. When he had finished both he rushed the drink up to Touko.

Avalon offered a hand to Mari's dad, "Hi! I'm Avalon. Me and Mari have kinda had a team since the beginning of the war. It's good to finally meet you."

"Oh, it's nice to meet you!" He shook Avalon's hand cheerfully, then leaned over to Mari and whispered curiously. Mari's face turned red and she grabbed the bolster pillow next to her, then rubbed it into Hideto's face as he laughed.

"I would be happy for you, though! Papa understands!"

"Papa can mind his own business!! Shit!!" Once the pillow was finally wrestled away, Hideto caught his breath.

"Byakuya, though..." He turned more somber, spinning the pillow in his hands. "The only time I saw the old man after I was 18 was when I tried to get my brother to leave. He hit the bottle as soon as he was old enough, to cope. I invited him over hundreds of times, but he said our father needed him." He leaned back, sliding the pillow under his head. "After a life like that... Shit, I hope he's in Hawaii talking to pretty girls by now. Anyplace better than that."

Avalon was confused, but laughed at the interaction between the two, "Yeah I don't know much about this Byakuya guy. Sounds like it was tough for him though."

Ayaka chuckled lightly. "Glad to meet you." She was happy to meet a Matou uncorrupted by Zouken's influence, even if she wasn't a proper Matou herself.

"Yeah, I feel bad for Byakuya," Yui sighed. "We tried to help him as best we could, but... Well, I hope he's doing okay too."

*****

"Ah! Thank you!" Touko took the coffee from Lazarus and inhaled its scent. "So! I'm told you're the sort of ringleader of this operation. I'm impressed you were able to get everyone to team up like this."

"I am too, honestly!" he sipped his own coffee, "Of course things haven't gone one hundred percent perfectly, but I feel like people are generally good and when given a chance to work together to solve an issue, they likely will. Even if sometimes they need a little push."

"That's good! I was a little skeptical about this whole Grail War thing, but you're doing a good job." She pulled the prosthetic from its case. "Anyway, I gotta get to work. I'll let you know if I need any help."

Lazarus nodded, left the woman to her devices, and continued his research after his lunch. He offered Hideto and Ayaka a place to stay with Tokiomi until the war passed if they wished.

"We've been set up outside of town already, just close enough for me and my wife to commute. We have a lot of mundane and magical defenses, too, so Ayaka will be safe." He rested an elbow on his knee, and his chin in his hand.

"'Sides, Zouken's the type to cut his losses. He might only try to get to you if he needs to use a command seal. Mari said your brother was controlling the Servant... Who could that be?" His eyes widened and he held a hand out as if measuring the height of a small child. "Shinji?? I didn't think he had any magical power!"

"Ah, yes," Ayaka replied. "No, he doesn't, but grandfather made a sort of fake Command Spell to let him control Assassin, but I'm still supplying mana to her. Anyway, I don't think he'll come after me. He didn't seem to care that I gave Assassin away. I think he's satisfied if he at least has someone fighting."

"I would like to stay nearby, at least. I might not be any good in a fight, but if you need me for anything, I can come and try to help out."

"You are such a sweet kid!" Avalon remarked, smiling, "Don't put too much pressure on yourself though okay?" she thought for a moment, "Hey can anybody spare a familiar? I don't make them well, but we could send one to watch over them maybe?"

"I can certainly spare a bird to watch over them," Yui said.

"That's so kind of you, to keep an eye on us!" Hideto grinned brightly. "Isn't it, Aya-chan?" Mari chuckled.

"Getting so chummy already?"

"Well good! Weeee should probably get back to work though..." Avalon bid goodbye to the guests and headed off to hit the books!

Mari escorted her father and Ayaka to the door. She lingered for a while, talking to Hideto in hushed tones. Before he left, they hugged, squeezing each other tight - the ink of Hideto's tattoo, the tail of a dragon curling on the back of his hand, mirroring the stark command seals of his daughter.

She went back inside with tears in her eyes, and a silent sense of resolve.

Just before bedtime, Yui calls everyone to discuss their research.

Results

Structure

The Greater Grail itself is like an engine, and the Lesser Grail is the key to start it up. While the Lesser Grail collects the souls of the Servants, the Greater Grail uses the energy to open a gateway.
Ichor leaks from the Grail when it is first being established. Its nature is a curse so strong that it is visible, so it can be called magical energy specialized for destroying people. It can not be practically used in any way, as it cannot be reshaped or anything of the sort. It stains anybody it touches with a strong curse and melts them as if they were being digested.
When the mud kills a person, the pain and fear felt before death remains as magical energy and becomes the next curse to seek out living people, thus making it capable of destroying the human race—not through sheer power but through rapid reproduction.
Heroic Spirits that come into contact with it gain bodies of flesh. The blackened Servant is incarnated by the power of the Grail so the more concrete ties to the physical plane turns them into powerful beings. Their physical interference power increases, but at the same time, they lose the ability to return to spirit form.

Theory

Heroic Spirit Summoning: The Grail makes contact with the Throne of Heroes and copies information from it. It then uses an incomplete form of the Third Magic to create an artificial soul, which is then placed into a "container," which is one of the seven Classes prepared beforehand.
Wish granting takes the form of only providing a massive amount of mana to the person who uses it. It takes working methodologies from the user’s mind and applies them to the wish. It’s not truly omnipotent or miraculous, but still very powerful.
The essence of its content is a "colorless force", but after the third Grail War, it has been polluted by Angra Mainyu and taken the form of a curse. It will interpret any wish of the owner with nothing else than destruction. The corruption is fundamental and it appears that inconsistencies cannot be corrected by precise calculations or interactions.
Additionally, since the corruption, the Grail has been able to summon evil-aligned Heroic Spirits; something that was not allowed before. The classes are, however, unaffected.
Update: After studying materials from the Einzbern Castle, Yui was able to determine that the Grail has containers available for the conditional summoning of at least 10 Servants, perhaps more. She wasn't able to find out what the exact conditions were for summoning extra Servants.

Conceptual Weapons

Since the corruption and the Grail itself are physically inseparable, a Conceptual Weapon might be required to cleanse the Grail. We suggest finding one that acts upon the concept of "evil" or "corruption." None of the Noble Phantasms they have applies, and they were unable to find anything else.

Destruction

Their research suggests a massive amount of power would be required to truly destroy the Grail, above what even Noble Phantasms can accomplish. Bazett suggested an ICBM or thermonuclear warhead could accomplish it, but collateral damage would be high.
It might be more prudent to dismantle it in stages, but our ability to work on the Grail safely is low. Rule Breaker may come in handy for dealing with the seals surrounding the Grail.