Another Option

(Matou house)

(Sakura)

"What happened?" was Sakura's first question as she surveyed her now-very-very-much-her's Servant's condition. The most obvious part being that she was straight-up missing her left arm, and the left portion of her torso and chest had probably regenerated a bit after being ripped open. The rest of her was a gauged and torn mess that probably included additional internal injuries.

"Caster took us by surprise," Rider responded through their now-unrestricted telepathic link. "It wasn't a spell either..."

The two of them looked at the girl Servant that she had dropped onto the ground near Rin's chair upon returning. "Why didn't you just drain all her blood and kill her?"

Medusa retrieved her blindfold from Rin and awkwardly tried to put it on before Sakura caught on and helped her. "Apparently the prana in her blood is very hard to absorb, or else she's simply extremely low."

Sakura just raised an eyebrow at the uncertain tone of Rider's analysis. "Either way, why not kill her if she's not of use? Or... maybe you can get everything by disassembling her inside the Bloodfort Andromeda?"

"Disassembling?" muttered the companion in her head. "Sure, Servants' bodies are made of spiritrons but- hmm..."

With her Master's help, Rider settled down into a something resembling a seated position on the floor. Nether of them paid much attention to all her blood which was visibly evaporating into prana that the Bounded Field greedily absorbed and returned to Medusa. Who commenced her explanation, "Your Senpai apparently had another ally besides Tohsaka. With a Saber, unless I miss my guess."

"Why do you think so?"

"Well, they were carrying a ridiculous sword, did not hide their presence at all, and responded when Emiya called him back for fear of Tohsaka's Archer. So class-wise, that's the only possibility."

"So why drag his Caster all the way back here? A hostage?"

"I'm thinking you might be able to negotiate with her. If what you said is true, then their timely retreat was probably her idea rather than his. If you can convince her I am still around, maybe it's possible to get her to, well, cooperate."

"Still around?"

"I'm basically done for," Medusa sighed. "I don't really have to explain, do I?"

"A Command Spell. I still have..." Sakura checked. "Two."

"Those don't work that way, unfortunately. I lack any useful healing or regenerative skills or Noble Phantasms. And there's still the question of prana, which you also need simply to survive." Rider shrugged, trying to appear unconcerned about her impending death. "I hope you're right about the boy. If so, at least you still have a chance."

Sakura paused and blinked away some surprise tears. Servants just return to the Throne of Heroes, she reminded herself, but it didn't help much.

Isn't this like when uncle...

"There is another option," a male voice suddenly broke into her despairing thoughts. "What?! Tell me."

"I've been taking a look inside your soul-" he paused as she frowned at the intrusion. "Hey, it's helping you now, right? Anyway there's an interesting Imaginary Number space, more like void, there."

"And how does this help Rider?" she snapped at the analysis. Void?

"She can't survive out here, even in spirit form, but you can probably lock her in something resembling stasis there. You'll still need to obtain prana, though."

"Assuming that's true, how would I get anything into a space in my soul?"

"She's a spiritual being, a familiar already bound to you as your Servant."

"More details, I'm listening..."

"Your magecraft, you may not have learning it consciously but nevertheless, we can utilize 'bind onto oneself'."

The worms? He had said that taking control of them herself might allow her to use the Matou magecraft sort of like, rather exactly like using a magic crest. "And how can I fit a whole Servant inside me?"

"Oh, I wouldn't worry about that. Fufufu-"

Sakura opened eyes that she didn't remember closing, and looked down at the crumpled form of Medusa resting almost peacefully at her feet. She reached down and gently shook the Servant back into consciousness.

"Onee-sama...?" Rider muttered incoherently. "No, it's me. Try to focus."

"Oh, I'm still alive," her Servant said in an almost disappointed tone. "What is it, Master?"

"There's a possibility," Sakura said quickly. "You're like a spirit, right? Please allow me to... bind you onto myself."

"Well, I don't really have anything to lose," came the reply after a brief delay. "I'm already all yours anyway."

Sakura tried to blink away several black lines that blocked her vision, before realizing that the long ribbons of shadow winding themselves around her Servant were quite real. Medusa didn't resist as she was dragged into a shadow that, unseen, had stretched out along the ground from Sakura.

"What are you doing?!" the magus exclaimed in worry at realizing she wasn't controlling the magecraft taking place in front of her.

"Don't worry Master," came the reply after a while. "I'll hold on tight, so she won't get away..."

Staggering out of the Bounded Field, Sakura gave in to the disgusting excitement of the crest worms that had responded to her use of them by eagerly seeking more prana, and vomited in the center of the room.

I should clean that up before Senpai gets here, assuming his new ally doesn't just kill me out of hand.

l

(A moment later)

(Rin)

Rin choked back a moan as her consciousness returned again, for she couldn't remember how as many times.

Sakura either hates me, or she really loves me and is totally crazy she mused as well as her cloudy thoughts allowed. It was much like being seriously sick. Of no help was Sakura's ranting, talking, whispering, whatever it was. Rin simply kept quiet or pretended to be in a daze whenever Sakura tried to elicit her attention, though that might be more because she was in a daze.

I'm probably running dangerously low on prana, warned part of her brain over Sakura's one-sided discussion about her fashion sense.

The other girl's sudden gasp and shift of gaze from Rin to somewhere behind her signified something, but before Rin could observe any more of the developing situation, she blacked out again.

When she opened her eyes again, Sakura was gone. However, instead of her captor was another familar figure. Rin awkwardly looked around to confirm that the two of them were alone inside the Bounded Field before speaking up.

"Sasaku?"

"Hmm yeah, what is it?" the Servant murmured, apparently quite at ease despite being in an enemy Servant's prana-leeching field. For a moment, Rin wondered if perhaps she was simply hallucinating.

"Are you... actually here?" she asked in a confused tone. "We need to get out, can you take down the Bounded Field?"

"Probably can," she replied completely seriously. "But Rider's on a timer since either Shirou-nii is on his way, or Shinji is dead and she'll be out of magical energy anyway."

"Shinji isn't her Master, Sakura is." The Caster blinked while taking in the information.

"That works out pretty well then, I guess."

"How so?" Rin demanded. Prana deprivation was certainly not doing such a number on her that she couldn't see something obvious. It was though - the answer floored her. "That girl will pretty much throw away even the War if Shirou-nii asks in the right way."

Well I sort of should have been able to guess that... she admitted to herself, before remembering their shared predicament. "Since that's the case, shouldn't it be okay to get us out of this?

"Rider might do something desperate if I did that," Sasaku said placidly. "Her draining Field isn't that dangerous to me. It isn't worth the risk."

"I'm dying here," Rin groaned in desperation, tugging a bit against the ropes that weren't really tightly binding her to the chair. "Even if you've got a Servant's resistances, you can't just sit there and watch me die."

The Caster smiles.

"I can."

l

(Sakura)

After cleaning up the mess, Sakura returned to find her two 'guests' apparently mid-conversation. Apparently Rin was crying? Rider guessed right, Shirou may have been Rin's ally, but not her friend. Or at least his Servant, at any rate. Good enough.

"Sasaku-chan," she said with a practiced cheerfulness that she definitely didn't feel, while extending a hand. "This isn't a good place, shall we discuss our business somewhere more fitting?"

As a Caster, Sasaku could probably break though the Bloodfort Andromeda, especially given how she had dealt with it earlier. Since Rider was not actually around to contain her, a combination of bluff and show of good will was in order.

"A circle of betrayal and deception. Haha-" She squashed the annoying chuckling.

Sasaku just smiled and took her hand without a word. A glance showed a completely pole-axed Rin. I wonder what they were talking about?

Leading the Caster, Sakura thinned the Boundary Field that she and Rider had collaborated on until it was thin enough for the two of them to simply walk through, leaving Rin alone to her thoughts.

The two of them sat on the only other piece of furniture in the room (besides the desk, anyway), which was her small bed. Sakura turned to the Servant and said as naturally as possible, "As we'll discuss magecraft and the War, I understand if you want to ensure our privacy yourself."

It was necessary so that Grandfather couldn't eavesdrop. Even if Sakura herself could do it, and she couldn't, the senior magus probably would be able to bypass it. Caster took the hint, nodding before responding with a low "Then, with your leave."

Almost as if this house is mine, rather than Grandfather's. A nice thought, if totally at odds with reality.

There was a faint tingle as prana spread around around the two of them. Sakura shifted uncomfortably as several of the worms inside of her responded to being suddenly isolated from Grandfather's influence. Because she had a part in putting up the modified Bloodfort, it seemed he was able to reach into it...

Sasaku waited for a while as the two sat in silence, before opening with a simple, "You know that Shirou-nii will show up any moment now?"

The magus frowned sourly, her thoughts of negotiation derailed. "We both know that I know you're his Servant, why keep the act?"

"Eh?" Caster seemed genuinely confused by the question. "I have all the paperwork though?"

"Wouldn't they be fakes that Tohsaka made for you?" Sakura shot back.

"Yeah." A shrug followed the admission. "Is this about her? Because we're not friends."

"I guessed as much. So, what did she do to tick you off?" Now we're getting to something good.

"Had her Archer rough me up, made me accept a geas scroll contract so she could control me - oh yeah, I guess I owe you one, so thanks." Sakura only looked at her questioningly until she volunteered, "It's something on a level of a Command Spell, but I guess your draining Field leeched from the connection so it... became unstable and broke."

"Wait, that's exactly what we need! Control..." Keeping her thoughts separate from her 'friend' was getting hard, but at least she didn't let it show. "Does this contract work on normal people?"

Caster didn't take any time to process the question or answer. "It seems magi in this age think it's an unbreakable binding, to the extent of one's soul." She outright laughed before continuing, "I'm sure you know that Servants don't follow the common sense of mortals."

"It would be like a magi to think they can control everything," Sakura agreed easily. "Can you...?"

"Unfortunately, I have no idea how to construct such a contract," Caster frowned. "But then again, since you already have Rin in hand, surely you can loot her house - there should be something there about it. I'm told she has been alone there for quite a while, so she can't have been taught directly."

Yeah, she's been there for a while, just smugly watching her domain. Sakura paused to consider the implications. Not about if taking the information on Tohsaka magecraft, but rather who should. She wouldn't be able to make use of it, and letting Grandfather get his hands on anything was as bad of an idea as... "Locking yourself up and throwing the key out of reach."

"I propose a trade: I'll lend you full access to all the Tohsaka material, if you lend me an appropriate amount of prana." As balanced as an offer as she could make. Or so she hoped it would be taken as, since there wasn't anything she could do to prevent Caster from just taking it all and leaving her, Rider and Rin for dead.

Well actually she might try to use the two of them for prana generation, but that meant Sakura wouldn't be useful once she found out about...

When Caster frowned, Sakura's heart sank, but instead of a rejection or threats, the Servant said "I can't transfer any magical energy to you. You must have noticed by now that it's hardly absorbed by your Field, or when your Servant vampired on me."

There was silence for a while before Caster spoke up again. "You need it for your Rider?" A quick nod was all the reply needed.

"That's my fault, I thought Shinji was her Master."

"He sort of was... Grandfather did something."

"I see."

"Can you draw from one of the leylines for me?" Sakura offered after considering the various sources of prana.

"I can't use it," Caster denied the suggestion flatly. "Is Rider drawing enough to actually kill you?"

"Ha- that might be the case," Sakura remembered how her uncle, and thus his 'strongest' Berserker Hercules had basically killed one another in such a way. That strength had to be paid for, and they couldn't run out on the bill. Lowering her head so that Caster couldn't see her face, she thought about how, even if she 'got rid' of Rider, the worms would probably still end up killing her and likely devour her corpse on their way out.

Caster sighed in resignation. "There is another option."

Sakura immediately caught hold of the proffered hope. "What is it?"

"You might be able to take it from Shirou-nii." Again with calling him that. Wait, she can't mean- her thoughts froze.

"He can't possibly have enough," she muttered numbly, trying to do the math on how many units worth of energy it might take. Which honestly she had no idea, besides probably a lot.

"I have some stores back home," Caster replied, though by the look of it she was having the same thought. "But anyway it's just a bottleneck issue, since you can get more output from Rin if you are able to let her walk about rather than sealed in a Field where she can't generate any usable prana.

"Ah, that's right." Things were looking up. "Information for prana swap, then we'll swap back later, sounds good?"

The two magi shook on it.

l

Notes:
Yes, Rin was facing the windows, with her back to the room's door.
As far as I can tell, while Servants can resist things like Command Spells, if you have a geas or such as part of your legend, you can't resist that any better as a Servant than a person because it really is written into your Saint Graph. Conversely I guess, trying to add one that doesn't belong to your Saint Graph probably doesn't work as well as one might guess.