Her sense of smell was the first to come in, as she took her first breath in over five hundred years. She kept her eyes closed, savouring the taste. Sweet, so sweet, she'd almost forgotten just how good the air could smell. Was this how it had been, before?

It couldn't last, and the stolen air rushed out in a soft sigh. When she breathed in again, eager to taste unsullied air again, it was too late. A tinge of acid, a sour chemical tang that was all too familiar. She sighed. It wasn't like she wasn't used to the taste of the tainted air she breathed out. Still, it was almost worth being summoned just so she could pretend she was only a girl again. If only for a moment.

Touch was next, as she felt cold smooth stone against her bare feet. She knelt anyway, lowering her head. Having never been summoned before, she didn't really know the correct rituals and protocols, but the closest thing to a Master was probably a client, and so she would show the proper deference. Opening her eyes – not that her Master would be able to tell, under the skull mask she wore as both identity concealment and badge of office – she risked a look around.

A church – or perhaps a chapel? She wouldn't know, naturally, although she had been tasked to kill more than one priest or bishop or cardinal visiting their 'holy land'. It didn't matter. Even if her Master didn't share her faith, they were still her Master. She peeked up, head still bowed, and looked at him.

Or them, rather.

Two people stood before her. One was a woman, with pale, pale skin, silver-white hair and red eyes. Not human, she saw. Not many would have noticed, but she had had to kill so many creatures that played at being human that the signs were obvious to her. A certain perfection of form, perhaps, that spoke of craft rather than the true creations of God. And the other…

A killer. Plain to see, for those who knew how. It was the eyes, dull and impassive as they may have seemed, that gave it away first. She saw how they roved over her form, and not in the way that most men's did. Face, then hips, then most of the way back up, yes, and she saw the minute widening of eyes, but it wasn't the lust she usually inspired and expected. This killer looked to her eyes for a first indication of killing intent, then to where her knives were kept. Then, rather than her chest – not that she was especially impressive in that area anyway – he watched her shoulders, in case she should suddenly attack.

And then he blinked, and simply regarded her impassively once more. She nodded. Yes. He would do.

She'd looked him over in almost exactly the same way, of course. The woman too. The woman was unarmed, but the killer had something hidden in the folds of his black outer garment (an overcoat, whispered the Grail in her mind), that from the size and shape was probably a modern firearm. There was also a knife strapped to his calf just above his right boot, and the rest of the pack of cigarettes was in the left breast pocket of his shirt.

It wasn't that she considered him a threat, or had any intention of poisoning his cigarettes. It was just that she couldn't help herself from noticing. She had been trained far, far too well to ever just see people as people and not threats or targets.

The killer raised his hand, showing his Command Spells, and she spoke for the first time – the oath she gave every client.

"Everything, everything, everything as you would will it. I will offer all of myself to you. This body, this heart, all of it…"

That done, she awaited her Master's reply.

"Your name and Class?" he asked.

"I am Hassan-i-Sabbah, your Assassin, Master."

Her Master nodded, as though he expected such a reply. "The Old Man of the Mountain, head of the order that gave their name to the word assassin. I suppose the legends have distorted with time. You are neither old nor a man."

"You are currently on a mountain though," said the woman behind him. When he turned to look at her, she grumbled, "Just saying."

"All the heads of the order, no matter their name before they were chosen, became Hassan-i-Sabbah," said Assassin. "Though, I do not remember what my name was… if you call me Hassan, I will be pleased to answer. It makes no difference."

"Well, we can't just go around calling you Hassan," said the woman in white with a pout. "That's not cute at all! Wasn't there anything else you were called?"

Assassin frowned, behind the skull mask. Whether or not her name was cute or not had literally never entered her head. She glanced at her Master, but he said nothing. Well, if he didn't disagree, she had no reason to disobey this woman, clearly an associate of her Master.

"When I was confirmed as the head of the order, and first took the name of Hassan-i-Sabbah, I was given a title to separate me from the previous head. He was Hassan of the Dreadful Wild, for his skill with beasts; I was Hassan of the Serenity, for mine with poison."

"Serenity…" said the woman. "What do you think, Kiritsugu?"

Her Master – Kiritsugu – gave a barely-noticeable shrug. "I had planned to simply call you Assassin, unless you have any objections." Assassin shook her head. "Then, do you object to Iri calling you Serenity? I doubt I can stop her, but if you really don't like it…"

Assassin shook her head again. "It makes no difference. Hassan or Serenity, I am still your Servant Assassin. I am yours to do with as you will – what you call me is a small thing next to this." There was no need for any attachment to a name that was never hers, after all.

Kiritsugu nodded, but the woman – Iri – groaned. "Ugh, you're both hopeless. I knew she was going to be like you, but I didn't think she'd share your boring pragmatism too. Kiri, I'm taking care of her. If I have anything to say about it, she won't turn out like you and be so dour all the time. We're fighting to save the world, for goodness' sake!"

There was just a twitch of a smile on Kiritsugu's face. "You realise that she's already dead? She can't 'turn out' any different from me, because her story was already completed centuries ago."

"Shh, you! I'm not listening to any more of your nonsense. Serenity, dear, come with me and we'll see if we can find you something a bit more cheerful than those dreary things you've got on to wear…" Iri made to take Assassin's hand – only to recoil when Assassin flinched backwards to avoid it, scooting backwards until she was a safe distance from her Master's partner.

Iri kept her hand out a moment, then dropped it down by her side, looking concerned. "Oh – did I scare you, Serenity? I'm sorry-"

"No!" said Assassin. "It is I who should be sorry. Master, Iri, it is important that you never, ever touch me. To do so is death, certain as sunrise." She drew her knees up against her chest. "Everyone who touches me dies. Even my breath will kill eventually. For your own safety, Master, Iri, please…" she forced herself to say it, "please stay away."

Illysaviel von Einzbern was in a huff.

These days, everyone seemed to be busy with something, and didn't have any time to play with her. Even Papa! When she'd asked what was so important that even the homc… the homuc… that even the maids were brushing her off, Papa had just got that uncomfortable expression he always got when she asked him about his work, and told her the news; that he'd be going away soon, along with Mama.

"But why?" Illya had whined.

"It's important, Illya. There's a lot of people who need help, and if your mama and I work very hard, we can save all of them. But we can't do it here, so we're going to have to leave. Just for a little while."

Illya pouted. Not because she was actually sulking – she was eight, not five – but because she'd worked out that whenever she did all the grownups, even Papa, were a lot more likely to let her have her way. She'd perfected it through years of trial and error, until the castle maids were basically putty in her hands.

It was technically lying, but it was with your face not your voice so it didn't really count, and it made it so much easier to get what you were after. (Illya took after her father much more than her mother, in almost everything but looks.)

"Can I come with you?" she pleaded. "I'll be really good…"

"No." And that was that. There was no arguing with Papa when he made that face, the one all hard and cold and scary.

On the off chance it might help, she'd gone to Mama as well, but didn't really expect it to work – despite how he looked, Papa was the soft touch most of the time. And, sure enough, Mama had just pulled Illya into a hug and told her to be good for Grandfather Acht while they were away.

Illya had agreed, obviously. It wasn't like she was planning to be bad for Grandfather, that was just stupid and the funny man from the Magus Association had gone home in pieces when he'd made Grandfather angry.

(Literally, in pieces. Still alive pieces, delivered one by one over the course of months. His head had gone last, and Illya had had great fun taking it on tours of the castle, especially once the lungs were disconnected and it stopped making that annoying wheezy screamy noise. Illya had sulked for days when the maids had gently but firmly pulled Prince Headward out of her hands and finally sent him home.)

Anyway, of course she wasn't going to make trouble for Grandfather, because she didn't plan to be in the castle at all. Papa leaving was bad enough, but he did that all the time and Illya had gotten used to it. Taking Mama, though? She'd be left with just the maids to play with, and they were boring. No, Illya was going, whether her parents liked it or not.

It wasn't quite true to say that Illya had never been out of the castle, but certainly she'd never been out of its sight. Still, going with her parents shouldn't be all that hard. Papa always took these big bags with him, and she knew they weren't the ones he packed his clothes in because he always made a game with her out of deciding what to wear on his trips. So they couldn't be anything really important.

Illya would sneak into Papa's room while he was out (she'd seen him talking very seriously with Mama in the study while looking at all kinds of boring-looking papers with little photos of people clipped on, and they looked like they'd take a while), and pack a bunch of her stuff into the bags. Then she'd hide in there just before her parents left, and by the time they realised she'd come along they'd probably be halfway there already.

Maybe she should take some snacks and books too, because Illya wasn't sure how far away this Fuyuki place really was. It could be a whole hour away.

The door to her parents' room wasn't locked – who would steal anything out here in this castle? – but Illya still felt like she was trespassing when she stepped in with a small bag of clothes and other travel stuff. There was a cold, creepy feeling in the room that she'd never felt before, even though the sun was shining brightly through the window.

Illya shook it off and marched in anyway. No-one was there, the room was deserted. It wasn't the time for the maids to clean, and they knew better than to wander in. No-one was watching her. Now, where would Papa put his other bags…

She found them under the bed – with how large it was, there was plenty of space. Grinning in triumph, she crawled underneath and started to drag the bags out so she could hide her stuff properly.

The bed creaked. Illya jumped, and darted out from under the bed and looked around. There was still no-one there. Eyeing the bed suspiciously, as though it was deliberately playing a trick on her, she retrieved the bags, and unzipped them.

When she saw what was inside, she huffed in frustration. The bags Papa always took with him were filled with guns. No fair – she wasn't allowed to touch Papa's guns, that was the one thing he'd ever ever shouted at her for.

So she needed some way of hiding herself and her things in the bag without touching the guns. Maybe there was some kind of pulley system she could rig using the bedsheets...

"You… should be elsewhere, child…"

llya shrieked and spun on the spot at the unexpected voice behind her. Her feet caught on the bag and she tripped, landing on her butt and facing the bed. Crouched on one corner like a spider was a grown-up, a woman with dark skin wearing a tight dark costume and a mask shaped like a skull. Illya scooted backwards until her back hit the wall, staring. The woman had definitely, definitely not been in the room five seconds ago.

"Ah, child… Illyasviel, yes?" said the woman. "Illyasviel, I am sorry for startling you. I work for your father."

Oh. Well, that did explain it. Papa did mention he occasionally worked with people.

(Illya liked to think of herself as pragmatic and cynical. However, it was hard to get good at being sceptical and spotting lies when you lived in a castle full of people who had no reason to lie to you. In fact, the only person who deceived Illyasviel regularly was her father, and then only in ways like going outside during a game of hide and seek and explaining afterward that they'd never agreed that it was out of bounds – despite Illya being forbidden to go outside without permission. So Illya was quite gullible, even for an eight-year-old.)

"Are you Auntie Maiya?" asked Illya. "That's the only person I know who works with Papa but she's never visited, because she and Mama don't get on."

"No. I am not Hisau Maiya. I am the Servant Assassin. You may call me Serenity."

"A Servant!" Illya's eyes shone, all previous fear forgotten. All Einzberns knew about Servants, of course. In many ways, the entire family was geared towards the summoning and use of Servants in the Holy Grail War. Seeing one in the flesh – well, spirit-flesh – was like seeing your life's work and also a superhero and a princess all at the same time. Then Illya made the connection. "The Grail War? That's what Papa's up to? Geez, he could have just said…" She crossed her arms, pouted (for real this time), and glared at the floor.

The Servant – Serenity – tilted her head. "Have I upset you? I am sorry…"

"No, it's not you – well, you made me fall over, and that hurt, but I'm not cross about that. It's because I definitely can't go with Papa and Mama now. I want to but… I get it. It's too dangerous." She lifted her head. "I'm hardly going to see them before they go, there's too much to do, and Mama won't be coming back, and Papa might- Papa might…" She sniffed, and hated herself for it.

Serenity paused, then lifted her hands to her mask and slowly removed it. Her eyes were huge and dark underneath, and full of concern for her Master's child. "Illyasviel, I will do my best to make sure your father is safe. While I am alive, none shall approach him without my knowing."

Illya smiled, eyes watery. "You'll keep him safe? Promise?"

"I promise."

"Pinky swear?"

Serenity frowned in confusion. "Pinky… swear?"

"Yeah!" Illya got up and crossed to in front of the Servant. "When you make a promise, and you link you pinkies, it's sealed for life. It's like a Geas, but it doesn't need any magic. Pinky swear you'll keep Papa safe." She reached for Serenity's hand, to show her, but the Servant pulled away, folding her hands under her armpits.

"That… would not be wise. But I can offer my oath, and my word. I will protect your father's life as though it were my own – as though it were more than my own. I promise, you will see your father again, Illyasviel."

Illya frowned sceptically. "I don't know. If it's not a pinky swear, I don't know if I can trust it. Let's see, let's see… oh! You're Assassin, right? That means you kill for money?"

"I worry about why you know that… but yes."

"Then…" Illya fumbled in her pockets, and eventually came up with a fistful of grubby change. "I'm hiring you! I know it's probably not a lot but… two Deutsche Marks, to kill everyone that's trying to hurt Papa?"

Serenity was still for a moment, mouth open in surprise. "Life and death are important things, Illyasviel, and not so cheap as that… but then, I have never taken a contract to protect another. Very well. The bargain is struck. Your father's life preserved, for two Marks." Serenity bowed her head. "I have never once broken a contract, lady Einzbern. I shall not start now."

Illya nodded in satisfaction. "Okay. Okay. If I can't go, you'll have to go in my place. Papa's very good at what he does, but he can't be all careful all the time." She drew herself up, and tried her best to sound regal, and impressive – like Grandfather when he addressed the family. "Watch him, protect him. You made a promise, we made a deal!"

At that, Serenity's lips twitched in a tiny, tiny smile.

"A troublesome Servant to handle, to be sure," said Jubstacheit von Einzbern, stroking his white beard. "One stray gesture, one careless touch, one moment of passion from either of you and your life is forfeit. Are you sure you're up to this, Magus Killer?"

"Yes." There wasn't anything more to say, apparently. The only sound in the old man's study was the dull roar and crackle of the fireplace, which cast everything in the grand old room into shadow and orange glow. Acht sat in his great leather armchair, while Emiya Kiritsugu had chosen to remain standing in the centre of the room. At the door, and standing almost unnoticeably by the walls, were attendant homunculi – servants and bodyguards both, with their heavy halberds within easy reach.

Here, in his place of power, the Einzbern patriarch was one of the most… unassailable men alive. As essentially a hired gun, Emiya was not allowed to go armed in his presence, and had left his Thompson Contender and Calico with an associate before coming to work for the Einzberns. That said, he still kept a personal handgun, and this he had surrendered to the waiting guards, who had locked it in a steel case outside the room.

This was more a gesture of respect to the man feared by mages all over the world, and more a result of Acht's understandable paranoia as head of one of the most distinguished magus families in the Association, than it was for actual security purposes. Even if the Magus Killer had been armed, the waiting homunculi would have run him through before he could even raise his weapon.

After all, Acht was very familiar with how his family's chosen weapon for the Fourth Grail War operated.

When Acht realised Emiya wasn't going to say any more, he chuckled drily. "Well, you would know best, I suppose. And how is the Servant herself? I will admit to… disappointment. I had hoped, given your reputation, for some great warrior who laid low many sorcerers and witches. St George, perhaps, or King Arthur… well, it can't be helped. Sometimes I think it may have been wiser for the Founders to implement the Relic system after all."

"I am entirely satisfied with Assassin. More so than with a hero. Our strengths match perfectly, as do our outlooks." Three facts, three statements. As ever, Emiya showed no emotion, even when arguing with his employer. Acht would have found it creepy, if he hadn't seen a hundred like Emiya come and go. However they acted, mercenaries were all the same. In the end, all that mattered was whether they turned out useful to the Einzbern family.

"As expected. That was why the Founders chose to have the heroic spirit match the Master, in the end." That, and at the time the Tohsaka and Makiri were set to become far richer than the Einzbern. Allowing any hero to be summoned by any master based on the relic they were able to procure would have turned the Grail War into a game of resources, or so the heads of the three families who created the Heaven's Feel Ritual had reasoned at the time. The richer family could simply acquire the greatest relics from the greatest heroes, and secure an advantage from the very start.

Instead, the summoning ritual was created so as to accept only one sympathetic link to select a heroic spirit from the Throne of Heroes – the prospective Masters themselves. Each Master called to whichever hero was closest to their own personality. Sadly, attempts to stack the deck by 'grooming' a candidate in such a way to attract a specific hero were futile. The Greater Grail awarded Command Spells as it pleased, and all such attempts had resulted in someone entirely different being selected as a Master.

Honestly, the Einzberns were lucky that Emiya Kiritsugu had managed to acquire the Command Spells.

"If you're satisfied, then I can only let you do your job," said Acht. "I do hope, for your sake, this Assassin is up to snuff."

"She is," said Kiritsugu.

"Really? From what you've said she seems lacklustre indeed, poison or no. I've no doubt she could take on every one of the family homunculi and win, but against another Servant, she'll stand no chance in a straight fight." The system that ranked Servants one against the other was ill-understood even by the Einzberns, who'd created the system in the first place, but it was possible for a Master to get a rough idea of how strong a given Servant was by using a form of limited clairvoyance.

Assassin was… underwhelming.

"Correct. That is why I don't intend to have her engage in any straight fights with other Servants."

Acht smirked. "You do realise this is supposed to be a Holy Grail War, Emiya? At some point you're going to have to fight someone. Even if you let all the other Servants defeat each other, all it will do is leave the strongest Servant standing. How will Assassin cope then?"

"Just like this, of course," Emiya said. He didn't gesture, but his eyes flickered to a spot behind Acht. Acht turned.

Standing directly behind his chair, hand outstretched as though to caress his cheek, was Assassin.

Acht stiffened in his seat. He was long past such undignified responses as startling or shouting in surprise – but his aging heart raced in his chest like it hadn't for decades. In the darkness, in her dark clothes, Assassin appeared as little more than a floating skull, grinning like the Grim Reaper himself.

How long had she been there?

For a frozen instant they remained like that, murderer and magus, in some macabre tableau, so very nearly touching. Then Assassin withdrew her hand, and retreated into the darkness once more, disappearing in a soft bloom of shadow.

Acht turned back to Emiya, and thought about how easily he'd been brought within a literal inch of dying. Inside his own room in his own castle, surrounded by combat-spec homunculi. Emiya stood there, saying nothing.

"I see your point," Acht said. "But mark me, Magus Killer – don't assume it will be so easy disposing of the enemy Masters. Unlike me, they will have Servants of their own. And each and every one of them knows that Servant Assassin could be coming for their heads. Not when, not how, but you've lost the element of surprise before the War's even begun. Simply striking from the shadows won't work forever. They'll know you're coming. They'll be ready."

"Of course," said Emiya. He held out a hand, and Assassin materialised at his side to place his handgun in it. The fact that it had been locked away under constant supervision didn't seem to have mattered, apparently.

"That's where I come in."

For each Master, a Servant. For each Servant, a Master.

Two reluctant killers.

Two aimless weapons.

Two dignified leaders.

Two dedicated protectors.

Two loyal nobles.

Two genius newcomers.

Two wild beasts.

May the Grail choose the worthy.