Rias Gremory. Heiress of the house of Gremory, school idol, king and devil, but is that everything she is? Soon enough, no. After accidentally finding a mysterious card in the library, she began studying the card, and the magic it was used for. The card was a servant-summoning-card, supposedly used during one of the mythical holy grail wars. The class of servant that would be summoned through the card was labeled as Assassin. On the specific card Rias found was the picture of two crossed daggers, with the letters J.t.R below the picture.
Standing in the Occult Research Club club room she began charging the card with magical power, before throwing it, activating the card and bringing forth the servant sealed inside of it. When it hit the floor, the daggers in the picture materialized, floating in the air. Then a silvery mist exploded from the card, filling up the entire room except for where Rias was standing. She could then hear a giggle from the mist, exact position unknown. She looked around the room, trying to find the giggle's exact location. Failing to do so made Rias finally run out of patience and as a result shout out to the mist.
"Whoever you are, show yourself!" Shouted Rias.
"As you wish." Answered the voice of a young girl, with a British accent (obviously). After the voice in the mist spoke, the mist began to gather by the still floating daggers, turning into the owner of the voice. A small girl, who couldn't be older than Koneko, in small black and red dress, made for combat, with the sheaths for the daggers on the sides of the legs. (A/N: Imagine the Assassin of black, Jack the Ripper, from Fate/Apocrypha in a black and red version of Asuna's main outfit during the Aincrad-arc from Sword Art Online. While I like the overall character of Jack, her outfit…not so much, so I gave her another (and in my opinion better) outfit.) This surprised Rias, as she didn't expect this.
"Who are you? What are you?"
"We? We're a servant, Assassin-class to be exact. And as for who we are… we believe that you saw our initials on the card we were sealed in. But to answer your question. Our name is Jack, Jack the Ripper. Now answer our question, are you our master?"
"Uhm…Yes." Answered Rias. That answer made Jack smile.
"Then let's make our contract official."
"Okay, but how?" Rias answer came in the form of Jack's contract-mark being burnt onto Rias right hand. Which hurt. The mark took the form of six knives and daggers in a fan-like shape. And as Rias screamed in pain, thanks to the mark being burnt onto her hand, the other members of the Occult Research Club rushed into the club room. All of them assuming the worst as none of them knew what had happened, they surrounded Jack, all of them ready to attack at any moment.
Jack on the other hand was mostly just confused, being completely unaware of who these people were. Instead of panicking, like most people would, she just tilted her head in confusion. Issei was the first one to do anything, which was to simply say:
"Who the hell are you, and what did you do to Rias!?"
"Yeah! What did you do to our king!?" Shouted Kiba. Koneko just glared at Jack.
"I'd rather hurry up and spill the beans if I were you, or this is gonna hurt!" Shouted a very worried and angry Akeno. Asia didn't say anything as she was somehow intimidated by Jack.
"Master, who are these people, and why do they look so angry?" Asked Jack Rias, completely oblivious of the fact that the others were ready to attack her.
"Everyone stand down!" Shouted Rias at everyone. "Allow me to introduce our newest member. By basic, she's a familiar of sorts. Why don't you introduce yourself? And these people are part of my peerage." That got everyone to back off, but not lower their guard.
"Okay! Our name is Jack. Jack the Ripper. Nice to meet you!" Exclaimed Jack, loudly with a smile, completely oblivious to the gasps and looks of shock she received from the others. Akeno found this very hard to believe.
"Alright. Enough jokes. Who the hell are you!?"
"We've already told you. We're Jack the Ripper, an Assassin-class servant. Specifically Master's servant." Exclaimed Jack while smiling and pointing at Rias on the last part.
"How does that explain why our king screamed in pain!?" Shouted Issei, who hadn't really been listening. He then noticed the mark on Rias right hand, which caused him to panic slightly. "And what's up with that mark on Rias hand!?"
"That mark is the sign of our contract as Master and Servant, specifically our mark, The Ripper's Six Blades. And as for why our master screamed in pain, we've heard that receiving the mark of a servant is a painful process. It supposedly feels like being branded by a branding iron. Not that we would know, we've never been on the receiving end."
"Your mark huh? Does that mean that every so called Servant has their own unique mark?" Asked Asia, who had gotten curious.
"Yup! Every servant has their own unique contract-mark. And you guys are?" Asked Jack the entire peerage, spreading out her arms to put emphasis on the last part. Seeing that they didn't trust her, she decided to reintroduce herself. "Let's start over. Our name is Jack the Ripper."
"Asia Argento."
"Akeno Himejima."
"Koneko Toujou."
"Issei Hyoudou."
"Kiba Yuuto."
"And I'm their king and your master, Rias Gremory."
"Nice to meet you all!" Exclaimed Jack with a smile.
AoG:JtR
During the following week since Rias summoned Jack had she been having strange dreams. What was strange about these dreams was that they felt more like memories rather than dreams.
In the first dream, she, or rather whoever these memories belonged to, had crawled out of a river in a very industrial city. After a few minutes of aimless walking in the streets, she met a woman. She then asked for some reason if the woman was her mother, but not in her voice. The voice belonged to Jack. Rias, or rather Jack, was only met with a beating. Becoming desperate, Jack lashed out, ripping the woman apart with a rusty and dull kitchen knife, which laid abandoned on the ground. And for some reason, she, or rather Jack, felt a strange form of comfort when she got soaked in the freshly spilled warm blood. After an unknown amount of time had passed said Jack something that caused Rias to wake up.
"Ah man. Now we're cold. We just wanna be warm." Complained Jack in a childish way.
The following nights were pretty much a repeat of the same dream, the only difference being the victims. When she asked Jack about it she learned that a Servant's Master always gets to see the Servant's memories in their dreams. When Rias asked Jack what the Servants original purpose was, she learned that their original purpose was to fight against six other servants of different classes in holy grail wars. But thanks to a certain wish, the grail was destroyed and the entire system around it collapsed, rendering it impossible to start new holy grail wars, but the Servants remained. All of them sealed inside of cards, like the card Jack was sealed in, being basically reduced to nothing more than superpowered Familiars. Jack honestly didn't complain though, she had a source of warmth and affection till the death of her master. When Issei asked if there were more Servants in the world Jack replied that she didn't know, since she had been sealed in her card for so long. She did however mention that there were hundreds if not thousands of Servants sealed inside of cards. Anyone from King Arthur Pendragon to Vlad "the impaler" III Tepes, a.k.a Count Dracula. Rias peerage was quite shocked when Jack told them that she wasn't the only Servant by the name of Jack the Ripper.
AoG:JtR
Another week had passed and Rias peerage had gotten used to Jack's presence. Though the rest hadn't noticed that Rias had been a bit down lately, Jack did. She really wanted to figure out what was wrong with her master, which she learned when a certain magic circle appeared in the club room, with a certain devil making a fiery entrance through it. When he was about to touch Rias, Jack decided to act. How? By jumping onto Riser's back, locking herself onto him with her legs, with a dagger at his throat and with another dagger dangerously close to his…junk.
"We wouldn't do that if we were you." She whispered into his ear. This caused Riser to panic for the fraction of a second.
"Hey, my dear Rias, who's the brat?" Asked Riser in a very rude tone.
"We can introduce ourselves. Our name is Jack the Ripper." Said Jack, whispering on the last sentence into Riser's ear. "This can go in a few ways. You walk out of here and never come back unharmed. You walk out of here without your…junk. Or you leave without your life. Your choice, now choose wisely."
Greyfia, who was normally very hard to surprise, was caught off guard by Jack's sudden appearance out of seemingly nowhere. It also rose her curiosity, as Rias had either forgotten to or hadn't told her or anyone else outside of her peerage on purpose about her new servant. She had however concluded that Jack wasn't a human or a devil either.
"Rias, who is the girl, and what is she for that matter?" Asked Greyfia politely.
"She's a so called heroic spirit, or a Servant. And as for who, Greyfia, meet Jack the Ripper. Jack, meet Greyfia." Answered Rias. The look of shock on Greyfia's face when she learned that Rias, her husband's little sister, had not only managed to summon a Servant, previously used in who-knows-how-many holy grail wars, and it was Jack the Ripper on top of it, was priceless to everyone.
"Hello!" Exclaimed Jack happily, without moving either dagger one bit, both of them threateningly close to Risers throat and his manhood.
"Could you please tell your servant to get off of Riser? Let's refrain from making things get out of hand."
"Fine. Jack! Back off!" Shouted Rias, reluctantly.
"Okay!" Exclaimed Jack before jumping off of Riser and make her way to the rest of the peerage. But not before making a fake attack towards Risers manhood, and making a "I'm watching you" gesture while saying; "We're watching you, ash-breath."
In the end, it was decided that whether or not Rias would marry Riser would be decided by a rating game, which sounded similar enough to a holy grail war to Jack. And she knew that that rating game would her best opportunity to show everyone what she was capable of.