Chapter One: The Worst Draw?

In the depths of the Matou Estate – not far from the writhing pit of crest worms the family called their specialty – Kariya Matou clenched his arm to his chest in pain as he completed the summoning incantation, the crest worms inside of him growing excited and the use of mana. A moment later he would instead clench his fist in satisfaction that it worked. In the interim he was slightly shocked that it had. The fact that he had shackled some hero of the past with a Madness Enhancement weighed on his mind as he braced himself for the rumored heavy load such a thing put on a master. However, as a tall figure in simple gray armor materialized, Kariya Matou felt no such burden. In fact one was lifted.

The man standing in the summoning circle in front of him spoke calmly. No, there was some annoyance there, but certainly not madness, "I ask of you. Are you the one that summoned me, uttering the incantation of a Madness Enhancement?"

The man was a knight. That much was obvious. He was dressed in plate armor. Clearly in was well made as well, and fitted specifically for the man. This was no low standing knight that simply won a set of arms in a joust, this man had been appointed. The problem was there was nothing about him or his armor that was distinct. It was just high quality medieval European knight armor. He could have been any knight in high standing from anywhere in any century of the era. His weapon was even just a simple, though quality bastard sword of no distinction. However, Kariya would later learn that heroic spirits only rarely carried their actual weapons on their belts in such a way.

Zouken was furious, "You useless whelp. You can't even do this simple an incantation correctly?"

Kariya cried out in pain as his father drove his staff into the leg the old man had just recently injured, "I DID IT EXACTLY THE WAY YOU SAID!"

The armored man calmly analyzed this response to his question and spoke, "So, am I to understand the man you are injuring is to be my master in the Holy Grail War?"

"Y-yes."

"Then perhaps the old man should stop injuring my master."

The clear threat was said so concisely and matter of factually that it was almost disarming.

Zouken was not an easily intimidated man, even by a servant, "I am the head of his House, Zouken Matou, and he is in this war as a representative of that house. So learn your place, servant."

"I will pay you due respect."

Zouken noted how deliberately ambiguous that promise was and it irritated the magus, "Who even are you? You're clearly a knight, and the catalyst was from Camelot; but you are so generic I can't tell what card we've pulled."

"The worst one, Zouken Matou. The very worst card you could have pulled. Now if you will excuse me, I must tend to my master."

The knight moved to Kariya, clearly going through the motions to lift him.

Zouken was not to be brushed off, "You will do no such thing. You will answer my question and you will let this failure of a magus walk out on his own."

"You used the Madness Enhancement yes? Then certainly you know what card you've drawn."

"A member of the most famous group of knights in history, made even stronger by madness enhancement. A berserker Knight of the Round Table."

"And you've pulled exactly that."

Zouken went to drive his cane into Kariya's leg another time to punish this insolence, "I asked you which o-"

The knight caught it, "Zouken Matou, take heart and heed that even if you summoned something as minor as the King's Hound it is strong enough to kill every person in this manor to the last and there would be nothing any of them could do to stop it. Now. I am a berserker class servant, and you are disregarding my polite suggestion to stop hurting the representative of your house in the Holy Grail War."

The magus was certain that was the most politely he'd ever been threatened with the deaths of his entire family before, "HA! A well spoken berserker? You truly are a screw up, Kariya. I'll leave you two to get acquainted, but this isn't over."

The knight watched Zouken's every movement until the old magus was out of sight. It was about then that Kariya flinched in pain again and spasmed at the wriggling of the crest worms in his body, once again eating at him.

"Sorry, about the old man, and the Madness Enhancement thing. He forced me into it. I'm not much of a mage, so he says I need every edge.'

"In your condition you can't handle a berserker servant's drain on your mana."

"There are crest worms inside me that make up for that. I just have to trade stamina for mana and I'm tougher than I look I swear."

"That's stupid." the knight had long since glanced over and seen the pit of crest worms not far from the summoning circle, "The Grail did not provide information of mage families of the era. Yours specializes in magecraft using crest worms?"

"Yeah. It's disgusting and abhorrent. They throw the heir into that pit several times a week and let the worms nest inside. Cultivates a strong mage if your body can take it."

"On that note, you haven't stood."

"Ha ha, yeah. I'm the only person in our latest generation with any magical talent and it's pitiful. Our once great house is dying out."

"Of course it is. Magical lineage is genetic and you're feeding your bodies to worms. I bet these worms would make fine mages."

"I guess that's what they were going for?"

"Idiocy if you are also killing off viable hosts."

Kariya rolled over to his back, "You have a point. It's one I've tried making. Zouken's solution was adopting from another mage family."

The knight finally knelt beside his master, "Ah, so the man is many levels a fool."

Kariya sat up sharply, "And a monster! We're talking about a child here! A little girl!"

"And you are in this war because you want to stop that?"

"Of course! You're a knight, surely the idea of doing that to a little girl repulses you too?"

The knight nodded, "So, Master, what is your plan?"

"Zouken was going to condition Sakura, the little girl, to fight in the next Grail War after this one. I promised him the Grail from this one if he'd let Sakura go."

"So if you win, he let's her go?"

"Yes."

The knight tapped Kariya's hurt leg.

"AGH! What are you-"

"He broke your leg, put your body in this condition, and made you summon the hardest class to maintain and control. One that has never even come close to winning because every other time it was called it either lost due to being dumb or killed the master through rage or mana cost."

"That's something that has me curious. Why are you none of those things? Are you really a berserker class?"

"Indeed. I suspect the nature of my powers has confined the Madness Enhancement to when I use one of my abilities."

"So I pulled a berserker that can turn it on and off?"

"Not exactly."

"Who even are you? I know you didn't take much of a liking to Zouken..."

"And he has certainly got any of the many forms of magical sensors listening to us right now, so I will not lay my cards out on the table to give him tools to use."

"Use? As in against you? You've been implying he's setting me up."

"You don't sound completely shocked. Which is good. That means you aren't as dumb as Zouken."

Kariya laughed, "I'm going to get along pretty well with you if you stop with the leg touching."

The knight immediately touched the leg again.

"HEY!"

Kariya suddenly realized that he felt no pain from the contact. In fact his leg started feeling better.

"Wait, you're a berserker Knight of the Round Table with healing magic?"

"Yes. As to my identity, I will share some information about myself. For one, you summoned me into my worst class as far as my abilities go. Though it does not suit my personality I only have full access to all my abilities from life in the Assassin class."

"Now I'm even more confused. A Knight of the Round that heals and has assassin-like abilities?"

The knight ignored him and continued, "I can't be summoned in Archer or Rider, and bemoan your poor choice of class if I need an anti-army Noble Phantasm. I only have one of those when I'm a Saber."

"You didn't mention lancer or caster."

"I don't have much affinity for lancer and if I were caster I would only have supportive magic. I am not locked out of either however."

"A knight that can't be a Rider...?"

"Like I said, you got the worst draw. Not only am I in the worst of the three classes I have real affinity in, you would not even have heard of me. Strange given several things about me; but we can discuss that later. I must tend to your body if we are to prove Zouken wrong. If I unleash that berserker ability with you like this I am likely to kill you."

Something occurred to Kariya, "Are you much weaker without that active? I'm not feeling much mana drain at all."

Tapping his master's newly healed leg, he energetically pulled Kariya to his feet, "You wouldn't anyway. Servants are only a large draw when they are active in the war. Certainly staying in spirit form and stopping the drain completely is the surest way to be in top fighting condition; and I may consider that if I must."

Kariya was impressed at the work. His leg was totally fine. In fact just in general he felt better than he had since before the worms were put inside him, "Wow. You did a great job."

Weirdly, the knight bounced up a little as if suddenly very pleased, "It is nothing. I am from the tail end of the Age of Gods if you recall. I am not Merlin by any stretch, but I am knowledgeable of supportive magics as I said."

"Good to know. Let's get out of here, you can check me for bugs... the listening kind, and then we can discuss what you can do."

"Indeed. Something we should cover before there is a risk of conflict of any kind. If we do get into a fight, I cannot guarantee that I will not activate that berserker ability. I will say it is not like a switch."

"Alright. I'll brace myself."

"Secondly, you are not a screw-up in this case. Even though you drew a bad card, I am indeed a berserker. I am sane because I have what is known as an awakened origin. Are you familiar with origins?"

"From my understanding every living thing is a piece of the Root, and your origin is an aspect of reality that defines you. It can influence your nature as a person."

"True. This is especially true if one is awakened to their origin. Such a thing usually grants supernatural abilities, but at the cost of being driven intensely by that concept."

"So for example f your origin was hunger you'd always want to eat?"

"Exactly. Someone with that awakened would basically be little better than a ghoul."

"Are you okay with revealing yours?"

"Totally. It will not reveal my identity because any knight could have it: Nobility. Save for the fact I could be lying about that; it means that I have to be noble. I cannot betray you. I cannot go back on my word unless it would be dishonorable to keep it, and other knight-like behavior."

"So basically, you have to be a knight?"

"Yes. The benefit is that because I am literally nobility, I gain immunity to nearly all forms of corruption and many forms of curses."

"So that must be why the madness was restricted on you."

"Exactly. Now with that done I must make this official." the knight knelt in front of his master, "Kariya Matou, if you would have me you shall be my master in this Fourth Holy Grail War and I shall grant your desire to save Sakura. Do you accept my oath of loyalty?"

Kariya nodded sharply once, "I don't know who you are, but I'm already honored. Now stand up, Berserker, and let's get to granting that wish."

Next Chapter: The Card that Was Dealt

Author Note: Chapter was a bit short I know and drops you right into events in progress within Fate/Zero, but it just felt correct to end it there and cover the rest later with more detail than would fit in the chapter length I prefer. Pardon any roughness, as I haven't written in years :(. Anyway, this story assumes you've actually seen the anime, and though things with change drastically in this fic it will keep assuming you know the original but I will describe settings more in the future. Next chapter this different Berserker's identity is revealed and the fate of Kariya Matou, as well as the rest of the Fate universe, abruptly changes course as the pair leave for the Grail War.