Disclaimer: I do not own any characters, names, and any copyrighted material used in this work. This is a fanfic, period. Everything belongs to their respective owners. Comments and constructive criticism are all very much appreciated.

Legacy of the Ancients: Evolution

Chapter 4

"That idiot…" Rin Tohsaka angrily thought as she heaved the cover off of the manhole and began to climb down. "...can't he read between the lines? His mother told him '…perhaps you should work with Tohsaka's daughter…' but no, he just had to rush in and be a hero. Hopefully he hasn't been killed or turned into a test subject before I get there."

Maiya Hisau had phoned her father and told him about Shiro's plans to investigate the strange happenings over the past week, and Tokiomi had reluctantly told Rin to go help him out. By the time she got to the rendezvous, there was no one there. After an hour of waiting and a boiling temper, Rin had gone in to check things out…only to find the tunnel blocked by collapsed debris a good distance in.

Thankfully structural analysis of the cave-in shows that he wasn't entombed under it. Unfortunately this means that I now have to find another way in.

Grumbling under her breath, Rin began to climb down the manhole, pausing only to drag the manhole cover back in place above her. "Whether or not a magus is behind this…" she growled at the foul odors in the place. "…I'm going to kill him for making a maiden like me enter this place. This is humiliating."

A few moments later and she stepped down onto one of the under-city's tunnels. Reinforcing her eyes and other senses, she cautiously pushed onwards. It wasn't long before she would encounter trouble.

As she entered a three-way intersection, insect-like sounds caught her attention moments before the sight did, as several spider women spat silk at her. They were fast…but so was Rin. As the silk flowed through the air towards her, she swiftly pulled out a wind-enchanted gem and threw it. The gem struck the mass of silk and exploded.

The blast of wind erupted in a half-dome fashion outwards, cracking stone and metal, and crushing the monsters which collapsed and fell to the ground twitching. Rin raised a hand to her mouth and fought the urge to retch as she saw how the monsters really looked like.

Human experimentation…I know things like that are inevitable when it comes to magic, but to this extent…bastard!

Rin looked around and then knelt to place a hand on the ground. She needed to know where to go, and the best way to find out which direction to go – given the fugitive being a magus – was to head for the strongest concentration of prana.

"Straight ahead, huh…?" she whispered as she stood, and headed down the tunnel straight ahead. The tunnel was surprisingly short, but Rin gagged as she reached the end and was forced to project and reinforce – otherwise it wouldn't last for long – a gas mask, considering that the tunnel apparently ran perpendicular to one of the city's sewers.

Ugh…what a wonderful smell our fugitive has discovered.

A sloshing sound caught her attention, and warned by instinct Rin stepped back into the tunnel and hid against the wall. After several moments her eyes bulged as she saw in the faint light of the service lighting a giant, humanoid abomination with three heads and a body that looked like it had been stitched together from God knows what appear and walk down the sewer.

What have we stumbled onto?

The thing stepped over the service bridge with surprising dexterity, and continued on its way. "Probably a patrol…" Rin thought as the thing vanished down the corridor, though she didn't fail to notice the cleaver-like blade holstered on its back.

Taking a deep breath – thankfully filtered by her mask – Rin stepped out of the tunnel and moved to cross the bridge. The mask vanished midway through, and it was a gagging Rin that made it across and walked up along the sewer edge – following the prana lines – to another tunnel.

She proceeded down the tunnel…and barely avoided a blast of rot vomited in her direction as she somersaulted backwards. "…what the hell?" she shouted, and retreated further as even more blasts of green and acidic slime was vomited at her, until at length she found herself back at the sewer.

The smell is terrible, but at least I have space around here.

Stepping to one side of the tunnel, Rin threw a piece of quartz into the tunnel behind her and closed her eyes. The crystal exploded with light, and a bloodcurdling scream echoed down the tunnel. She smiled; considering the darkness down here that blast of light would have blinded it.

Opening her crest, she stepped into the tunnel entrance with her right hand facing down the tunnel palm outwards. "Eisen, feuer, und stein…" she cast, her crest glowing blue in the darkness and illuminating the hydra-like monster writhing in agony, its bulbous eyes bleeding heavily. "…Zweihander!"

A blast of prana ripped from her hand and blew the monster in half before continuing down the tunnel. Rin sighed as she lowered her arm, and then glanced sharply to the side at the sound of heavy breathing echoing down the tunnel along with the sound of splashing water. "Oh shit…" she cursed, and then she ran down the tunnel.

I'd forgotten that I wasn't alone down here. All that light and noise was bound to draw something's attention.

Rin ran down the tunnel, and briefly took a moment to rest as she reached its end. Judging from the frustrated roars behind her, whatever abomination was pursuing her was too big to fit in the tunnel.

That was just fine.

Rin turned to the right to follow the source of the prana, only to curse as she realized that her earlier spell had caused the tunnel there to collapse, and forcing her to proceed down the left-hand tunnel and hope that it too proceeded to where the prana was coming from. The tunnel was surprisingly long though, and Rin wondered at its length after ten minutes of walking. A pinprick of light appeared at the end, and Rin tensed as she wondered whether or not it was a sign of danger.

The light grew stronger as she approached, and Rin relaxed slightly at the realization that it was just artificial lighting. As she exited the tunnel, Rin briefly took in her surroundings: a well-lit room with a section of one wall dominated by a bank of gauges and switches, and another section by a series of pipes and valves.

She barely had time to take this in before she leapt forward, narrowly avoiding a wafer-thin projectile of red solid, but considering the speed it had been sent against her it would probably have run her through with ease. She looked up and gagged.

It was probably a Human once, and it still looked Human. That is, if one ignored the glowing glass eyes and the mechanical lower half of its face. Rin shuddered as she dodged another salvo, and found herself thankful for the black cloak that covered its body.

God knows what else could be wrong with it.

The thing raised its hands and pointed them at her palm outwards, and Rin snarled as she somersaulted around the room, the thing bombarding her with impunity from the service section above. She pointed her finger and returned fire with Gandr…to no effect. It didn't even try to dodge, and tanked her attacks for all the good it did her, all the continuing its own attack.

Whatever was done to it probably renders Gandr's curse ineffective. But it doesn't seem inclined to dodge...if that's the case then…

As she continued to avoid its attacks, Rin pointed her finger at a pipe and fired a Finn shot. The pipe buckled and a high-pressure jet of water spurted out. "…that'll do!" she shouted triumphantly as she evaded a fresh salvo – belatedly realizing that they were probably made from crystallized blood or ichor – and reached into her crest.

With a gesture, a stream of water split and froze into a spear-like form, and with another gesture, impaled itself with extreme prejudice into the monster's head. It froze, and then toppled forwards and fell head first onto the ground. Rin winced and gagged as the head burst like a ripe melon against the stone floor.

She made another gesture and a sword of ice formed and floated to her hand. "I'm a bit rusty with the sword…" she muttered. "…but this might be useful."

Kirei Kotomine was not a happy priest.

Well perhaps that was a bit confusing. Kirei had his issues, in particular a burning obsession to know why he enjoyed the pain and suffering of others so much. But that didn't stop him from enjoying life, at least not anymore.

The days were spent preparing platitudinous homilies for the small Christian community in his care, maintaining the façade of cooperation with the Tohsaka, keeping himself fit, and finding ways to amuse himself. These ways usually involved television and eating hot and spicy food.

Outside of certain situations, mundane Humans make for better entertainment than magi.

There was also his professional relationship with the victors (by default) of the Fourth Holy Grail War. But they and their adopted family generally left him alone to do as he pleased, although Sakura Matou had put her foot down regarding some issues.

It's funny how a girl who heartlessly tortured her birth-mother would care so much about her elder sister, even if said sister has closed herself off from her.

Well, it wasn't like he had any real need to silence either Rin or Tokiomi, so there wasn't any problem there. With no issues on the supernatural side of things, a monotonous and surprisingly relaxing lifestyle on the mundane side, all in all Kirei had every reason to be content.

And then this fugitive just had to come in and spoil it all. Both Tohsaka and Emiya – whom Kirei had ignored as the broken Kiritsugu wasn't really as interesting as he was when he had been the Magus Killer – had gotten involved in the matter. Tokiomi had 'requested' that he go help Rin and that boy Shiro Emiya out, and it wasn't long before Medea had called him.

Get rid of him.

Black Keys flashed through the thick air as Kirei swept down the tunnel, his arms and legs blurring as he lashed out. Conceptual weapons expertly sliced limbs and heads from bodies, even as more physical strikes pulverized bone and liquefied internal organs.

This is below me.

The things he was facing were nothing more than puppets, cyclopean constructs of Humans flesh with fanged mouths and clawed hands possessed of wiry strength and inhuman speed. Mundane Humans and unskilled magi would probably have been overwhelmed by sheer weight of numbers…but individually the things were weak. Mundane Humans armed with modern weapons and most magi would have torn them apart.

He was an Executor. These things were nothing compared to Dead Apostles.

Kirei didn't really blame Medea for sending him to 'get rid' of trash like this. As far as she knew it was just another magus. She couldn't have known that he was holed up behind these pieces of shit. It was the fugitive who was demeaning Kirei by making him fight these dolls.

I am going to kill him slowly and painfully, all the while enjoying each and every excruciating moment of it all.

The last of the puppets fell dead at his feet, and Kirei exorcised some of his frustration by crushing the corpse's head beneath his boot. Stepping forwards after gathering his breath, the priest kicked down the door leading to the next gallery.

A bounded field fell into place as he passed into the room, seemingly-trapping him in the room. At the same time it began to fill with gas. Stun gas probably; whoever was holed up in the under-city would most likely want to interrogate whoever could get this close. The priest rolled his eyes.

This trap was pathetic.

Kirei threw a Black Key and collapsed the bounded field and simultaneously blew open the door leading out of the gallery. And then he calmly walked out the room as it slowly filled with gas, his lips curling into a smug smile.

Damn, I'm badass.

Surprisingly the gallery didn't lead into another tunnel, but rather into a narrower and longer gallery. It was well-lit too. And he wasn't alone. Four gigantic figures towered before him, multiple heads leering malevolently down at him from misshapen bodies.

Is this supposed to be some kind of joke?

With a roar one of the giants swung a cleaver-like blade at him. Kirei dodged backwards, a Black Key striking the giant in the head and blowing a chunk of it away. The monster roared in pain and fury, and Kirei blinked in surprise at the fact that the Iron Plate Effect didn't kill it outright. He smiled.

Perhaps this wasn't a total loss after all.

"What the hell are these things?" Rin screamed as she used Gandr with both hands, mowing down…the things swarming towards her.

They looked like children, except they weren't children or Human. Well they might have been the latter at one point in time, but Rin refused to accept that fact. She just couldn't.

Magic…magecraft is the study of miracles. It is the process of uncovering the secrets of the world and using those secrets to create miracles and to better the lot of Humanity.

Their skins blackened with ichor and their limbs deformed into spindly, claw-ended extremities, those things weren't monsters. They were abominations. Their sharp teeth dripped venom, and mindless, crimson eyes saw her as prey. "Damn it all!" she screamed as she jumped back and threw an entire handful of fire and wind-enchanted gems at them before running out of the 'nursery' and taking cover behind a wall.

The explosion shook the walls and ceiling, and blew bits of ichor and flesh out of the ruined door. After several moments of heavy breathing, Rin risked a glance back inside. She sighed with relief at the confirmation that nothing alive remained inside.

This…this is horrible…

The young magus slid against the wall down to the floor, breathing hard. As she advanced deeper into the fugitive's stronghold, she found more than one chamber or gallery that left her shaken to the core. The 'nursery' was simply the latest of them.

One chamber had several surgical beds inside, over which loomed mechanical constructs that resembled humanoid spiders. They were inactive, but Rin had quickly realized that their limbs had terminated with tools meant to take flesh apart…but not to put it back together. Shaken by the realization, Rin took them apart viciously.

One other chamber had been the worst, clearly catatonic women stripped naked and with a variety of pipes and tubes plunging into their flesh from the beds they lay upon, and below their waists…no, no, no! She didn't want to remember! She didn't want to remember or to think about what had been done to them, or the fact that she'd put them out of their misery.

A pit full of worms and a black-eyed man dragging a younger girl and a mirror of herself towards it.

"Sakura…" Rin breathed. "…is that what almost happened to you? Is that why you killed mother? God…why…why did this have to happen? Magic…it isn't supposed to be used like this!"

Shakily rising to her feet, Rin continued on her way deeper into the under-city. The rest of her explorations passed in a blur, though later on she would vaguely remember facing and fighting and killing other abominations. Things that looked like crosses between scorpions and cockroaches…a centipede-like construct of deranged Humans fused to each other in ways that should not be possible and were complete perversions of the sacred art…she even remembered vomiting as she came upon a pit filled with blood, shredded flesh, and broken bone.

This…what is this place? Not even the darkest tales of the cruelest and most vicious of the Dead Apostle Ancestors were this bad.

She should have fled, turned back, and gone for help. Kirei could deal with this. Sakura probably could too. Her mother…Aunt Medea…wiping this hell clean would be child's play for her.

But she kept on going.

Emiya-kun, are you still alive? Are you still you? Where are you?

"Marvelous…" the Viscount said with approval as he walked around his workshop, and Shiro Emiya defiantly glared at him from where he'd literally been chained to the wall. "…truly a marvelous specimen…do you know what this means boy?"

"No…" he said angrily. "…and I could care less."

The Viscount sighed. "You have so much potential…" he said mournfully. "…even if your number and quality of magic circuits are all average, with an aligned affinity and origin of 'sword' your potential for performing magecraft is unimaginable! Come now boy; as much as it pains me to admit this, you are unsuitable to simply be used for my art. No, you could be an artist yourself! So how about it: won't you become my apprentice? Together we shall immortalize ourselves with our combined talent!"

"Screw you!"

The Viscount sighed again, and picked up what looked like a bone drill, causing Shiro to blanch in alarm. "It's such a shame then." He said. "You have spirit in addition to talent, but it is untamed. It lacks purpose and awareness. But I will not suffer this, that such talent either be wasted or worse, corrupted by those weaklings from the Clock Tower. You will be my apprentice, one way or another."

Shiro began to struggle, and the Viscount chuckled. "There's no point in struggling." He said. "Those chains are specially-forged to restrain magi. Well, I suppose it's possible to overload them, but at the moment your lack of training along with your rather average base magical potential makes that impossible. Now then, shall we begin?"

Shiro glared defiantly as the man approached, a bone drill in one hand and a scalpel in another.

Is this how it ends? Alone and helpless, to lose everything I have without changing anything?

As if in reply, a massive explosion shook the room as a deep and powerful rumble could be heard echoing. The Viscount Valier looked around in alarm, and a reptilian familiar sped into the workshop and quickly crawled up its shoulders. "It would seem that more interlopers have come…" he said disdainfully and placing his tools back on a nearby desk. "…no matter, I'll deal with them real quick. Fighting is such a waste, but at the very least I might be able to get some interesting material to work on."

The madman stormed off and slammed the door behind him, and Shiro resumed trying to break free. "…fundamental structure analyzed…composition reinforced…"

Reinforcement was a rather simple form of magecraft, but it could be surprisingly difficult to use. It involved using prana to 'fill in' the 'gaps' of an object's fundamental structure, reinforcing its base attributes and increasing them. And that is where the difficulty lies: should the reinforcement process be flawed, then the object would reject the prana, and self-destruct.

And by deliberately messing-up his reinforcement, Shiro hoped to break free.

It didn't work. The boy cried out as the chains threw his prana back at him, the backwash in his magic circuits resulting in agony. However Shiro knew pain. This was just an annoyance. "One…more…time…" he whispered…and then the wall on one side of him exploded inwards much to his surprise. "…what the…!"

A dazed girl walked in, her eyes weary and slightly-crazed: Rin Tohsaka.

"Tohsaka…!" Shiro shouted with a mix of relief and surprise. "What are you doing here?"

Rin blinked and turned to look at him. She looked blankly at him for several moments, and then she blinked a few times as greater awareness returned. "E-Emiya…?"

"Yeah, it's me!" he said, and then he tugged at his chains. "Look, can we save the talk for later? The madman's run off for now, but I don't know when he'll be back, so can you please get me out of these chains?"

Rin blinked, and then ran over while pulling a gem out of a pocket. "Right, right…" she began while fiddling with the chains. "…we'll talk later. For now let's get you of those, and then finish that bastard off!"

A/N

I don't really have much to say for now.

Scratch that, I have something to say after all. Actually yes, Kirei would be disgusted by what the Viscount is doing. Kirei's a piece of work, but even he has lines he won't cross. This is a guy who stabbed Tokiomi in the back and manipulated Kariya and Aoi into destroying each other in canon...and is profoundly offended by Zouken's very existence.

So yes, even his AU self would be disgusted by what's happening under the city.