Author's Notes:

Hey! Everyone! Hope you all have a good day… Now then I'm going to write something different… Now, I have been inspired by the Fate Grand Order New Order series by Pheles65, and I can't help but wonder if there was any other worlds that Ritsuka and Mash can travel into. This will also have Elements of Kingdom Hearts also.

Now then this has nothing to the King of Time and Humanity's Last Master series, Here this title will be called Fate Grand Order: Crack Between Dimensions: Mythos. And as it says this will be crossover between the Riordanverse and Fate Grand Order. And in this Fanfic Ritsuka and Mash are just about to spend their peaceful days. When Zelretch, and Aoko contacted Arcueid in Chaldea who then explain to her that they are now being pursued by a bunch of hooded figures who had the ability to traverse to other dimensions. Where they then started to go to many different dimensions causing distortions that need to be fix. With the first one being an alternate version of America that is occupied by the Greek, Roman, Norse, and Egyptian Pantheons.

Disclaimers: I don't own any of the characters that have appeared in this fanfic. They belong to their respective creators: Kinoko Nasu, Takashi Takeuchi, Type-Moon, Disney, Rick Riordan.

Prologue:

The Beginning of a new story

3rd POV

Inside a mysterious Castle

2023 AD

In a dark creepy forest whose trees rustle with a howl of an owl, a lone figure ran as if it was late. The figure then opens the gate and doors. And inside was a vast hallway decorated with paintings and statues.

The figure was a middle aged man with a black cloak, he then went inside and started to walk down the hallways. As he walk, he felt a presence behind his back.

"Can you cut it out with your habit of always staring at me…" As soon as the man said this, a girl with red hair, blue eyes and wearing a white shirt, and blue pants and the way that she looks at him is a cheerful look, "My… you really are such a killjoy."

The man sighed, "Please, I'm only just trying to help you let go of that attitude of yours. Aoko."

The girl chuckled, "My… Sorry my bad…" She then continues to follow the man as he opens the door. Inside of it was a room that was filled with bookshelves and many other magical and scientific contraptions.

The man the lifted his robe revealing a face of an old man with grey hair and red eyes, "I'm trying to focus on my latest project. So, please just leave me be."

"Okay, I understand, Zelretch…"

Aoko then left the room by disappearing out of thin air, "My goodness, that girl is such a handful." He then started to do some light reading.

However, as he was about to turn the next page, he heard an explosion from across the living room with Aoko bursting to the room and locking the door. She then starts

"What—Aoko what is happening?!" Zelretch asks the redhead.

Aoko replied to him, "It's them! we need to get out of here!"

Zelretch sighed in exasperation as he knows who Aoko was referring to, "Ok, ok I'm coming!" He then gets up from his chair as he heard voices, "VAMPIRE! YOU WON'T BE ESCAPING FROM US THIS TIME!"

"Tch…" The old man then went inside the teleportation spell. As the door was about to be destroyed. They disappeared causing the assailants to be really angry with the middle one yelling out loud

In the middle of the forest

Present Day

As they appeared in the forest, Aoko then asks Zelretch, "What do we do now?"

"We have to contacted 'her' and 'them'…" He replied to Aoko who widen her eyes at this. As she knows who Zelretch is referring to at this moment.

"But Zelretch they just come back from the Lostbelt incident!" Aoko exclaimed.

Zelretch smiled mischievously as he replied, "Don't worry about it… I'm sure they will agree…" They then disappeared as they go to another location.

Ritsuka POV

Inside the Chaldea Security Organization vessel Storm Border, Antarctica

2023 AD

Meanwhile, we turn our attention to the Storm Border which was a ship that look like a Cruiser inside white halls adorned every space with windows also there, in the years following the Lostbelt incident. From whichChaldea had to deal with the complete bleaching of the earth as well as resolving a few incidents. The Mage Association and the United Nations negotiate with the staff. With Vice Director Lorelei Barthomeloi, Chaldea Director Goredolf Musik and Sion Eltnam Sokaris come to an agreement that Chaldea will become a Peacekeeping Organization much to the protest of the Mages who want to keep the masquerade.

This nearly escalated until Lorelei established rules that satisfied both parties:

Rule 1: Chaldea will not participate in any Global conflicts unless it's absolutely necessary.

Rule 2: Rayshifting and Zero sailing can only be undertaken when the Director gets permission from the Association and UN.

Rule 3: The Servants must keep their identities a secret. Unless the Master or Director permits it to be revealed.

Rule 4: Chaldea will spread out around the world and establish hideouts so that it will have a quick response as well as easily manage the staff and Servants.

As soon as the rules are established, Ritsuka then resummoned the Servants that he met throughout his journey. With Mash and the others being present. And when the servants appeared, he then organized them by sending them to the selected countries. With the corresponding Servants as leaders, examples being:

Oda Nobunaga and Hinako Akuta/Yu Mei-Ren in Japan.

Europa and Iskandar in Greece.

Thomas Edison and Geronimo in North America.

Artoria Pendragon and Morgan in Great Britain.

Ozymandias and Nitocris in Egypt.

As we go inside a room, we saw a black-haired man wearing a white uniform he was now waking up as he open his eyes which were blue in color, this is Ritsuka Fujimaru the Master of Chaldea he look at his surroundings as he muttered, "Man, that was one hell of a good nap…" He then gets up from his bed as he starts to walks into the halls, he then noticed a small white creature coming towards him.

"Oh, hey Fou…"

Fou then goes to his shoulder as they continue to walk, they heard footsteps with a girl's voice calling out to them, "SENPAI! FOU-SAN!" It was a lavender haired girl wearing what appears to be a parka, a red tie, and glasses her hair also hides her right eye. This is Mash Kyrielight the vessel/Pseudo-Sister of Galahad the Grail Knight.

She then went towards them and said, "Do you have a good night's sleep?"

"You could say that… What about you, Mash?"

The girl Mash looks at Ritsuka with a smile on her face as she joins the two as they continue walking down the hallways, as they continue to talk. They heard a Male voice calling out.

"Mash wait up…"

They look and saw that it was a boy around Ritsuka's age with white hair, wearing black and purple armor, he has a sword on his side. This is Galahad the Knight of the Round Table, after the Lostbelts Chaldea has found a way to separate both Mash and Galahad. Creating a replica body and placing Galahad's core into it, caused Mash to be a normal girl, and that she can only regain her powers whenever Galahad chooses to merge with her again.

"Onii-san!" Mash smiled.

Galahad sighed as he didn't want to be called like that by Mash seeing as she was not really his sister, "Mash Kyrielight, how many times do I have to tell you not to call me that!"

"Oh… Come on, don't be like that…" Mash smiled.

Ritsuka chuckled at this, ever since Galahad was extracted from Mash the latter starts to treat him like a brother. However, the Shielder still considers her just a little girl.

Ritsuka then interjected, "Now, now, Galahad just try to be nice…"

Galahad sighs, "Fine… I'll be polite…"

Suddenly another male's voice called out, "Fujimaru! Mash!" They turn to the voice, and it was another boy around Ritsuka's age with ashy white hair, orange eyes, and a face that looked like he didn't get some sleep for weeks, his attire consist of a white winter jacket and black gloves, and white pants and shoes. This is Kadoc Zemlupus a former Crypter and fellow master of Chaldea.

"Woah… Kadoc, why are you in such a rush?" Mash said.

Kadoc then starts to calm down as he starts to speak, "It's Archetype, she wants to speak with you!"

"Arcueid? Why… What happened?" Ritsuka asked.

Kadoc sighs, "Just come with me, she will explain right away."

The three nodded as they followed Kadoc to Arcueid's room. As soon as they are in front of the door of Arcueid's room. Kadoc looks at them, "Okay guys, you ready?"

"Yeah…" Ritsuka replied. They then went inside to see a young woman with blond hair, red eyes wearing a white and blue ballgown, with white sleeves. This Archetype: Earth AKA Arcueid Brunestud a Moon Cancer Servant as well as the Moon Princess.

"Master! I'm glad you're here…"

Ritsuka then replied, "Woah! Woah! Calm down! What is it that you want to talk about, Arcueid?!"

The Moon Princess then inhales and exhales as she then sits down on a chair with the others following suit.

"So, what is it?" Mash asked.

Arcueid then begins to explain, "It's Zelretch, he contacted me in a dream!"

This caused Ritsuka's group to be surprised, "That old coot? What does he want now?" Kadoc asks the Princess who then lowered her head as she darkens her expression.

"Well… He told me that he and Aoko are being chased." Arcueid answered.

The four were shocked at this with Mash asking, "But who and why would they want to capture them?"

Arcueid shook her head, "I don't know but it sounds like this has something to do with his Second Magic as well as Aoko's Fifth Magic."

This caused Ritsuka's group to be widen their eyes, "What do you mean by that, Arcueid-san?" Mash inquired.

Arcueid sighed, "It's because the enemy has a mysterious power that is similar to the Second Magic…"

The four have become more worried about all this, "Are you serious?" Kadoc exclaimed.

"Of course, I am!" Arcueid shouted she then tries to relax as she inhales and exhales as she was about to continue. They heard the red lights ringing as if there was an emergency as well as hearing booms from outside.

"What the— What is all that noise!" Galahad said.

"It must be Da Vinci!" Kadoc exclaimed.

"Fujimaru! Mash! We have an emergency!" A little girl's voice called out.

They then look at each other, "I believe we just find the answer we are looking for." Kadoc muttered. They alongside Arcueid got outside the room as they ran through the halls, they look at the windows and saw red skies and cracks opening, "What in the world is that?" Kadoc muttered.

"I don't know… But I'm pretty sure it is not good." Ritsuka said. As they continue to ran through the halls, another explosion roared through the halls. They then saw that a group of Ritsuka's Servants consisting of James Moriarty (Archer of Shinjuku) who looks like a gray haired old man with gentleman's clothes a blue cloak, glasses, and is using a coffin gun, Edmond Dantes whose appearance is that of a young adult with a green trench coat and a green hat as well as messy ashen hair and yellow eyes.

Their opponents looked like a bunch of skeletal warriors as well as sphinxes, giant cobras, and a pair of men with clubs and skull bull masks.

"What the—" Kadoc exclaimed.

"Are those Moriarty and Dantes?" Ritsuka asked.

They then saw James Moriarty shoots at them, with Dantes following suit by shooting lightning bolts. As they destroyed the enemy, they saw Ritsuka's group with Dantes calling out, "Master!"

"Moriarty! Dantes! What is happening here?"

Edmond Dantes then answered, "That's what we want to know! We were just minding our own business, when this cloaked guy showed up and started to ransack the headquarters."

"It's a good thing most of the Servants that were here act accordingly. Or else we would have been screwed like last time." Archer Moriarty agreed.

Ritsuka sighed in relief but then realized something, "But what about Da Vinci and the others?"

Dantes then replied, "They are safe at the control room, but the enemy has them trap…"

Mash gasps at this, "If that's the case then they need our help!"

The others then nodded as they and Mash joined the two Servants as they ran towards the control room.

Sion POV

Inside the control room, Storm Border, Antarctica

2023 AD

Meanwhile inside the control room, which is filled with boxes and coffins, another group of Chaldea staff members and Servants are now fighting back against the enemy against the enemy.

The staff members consists of a young girl who looks like a girl version of the Mona Lisa with blue eyes, wearing what appears a ballgown with blue, brown hair, and white colors, a girl with purple hair and glasses and is wearing a purple beret and is wearing a purple blazer school uniform and a white skirt and a fat man with blonde hair, moustache and is wearing a white generals uniform. These are Leonardo Da Vinci (Rider), Sion Eltnam Sokaris and Goredolf Musik.

As for the Servants they consists of a young woman with blue eyes and blonde hair with a metal headband. Her attire consist of a blue dress with armor and a rapier in her abdomen she is holding a flag in her right hand, the second was a young man with blue hair wearing a gentleman's clothes. And lastly the third one was another woman with purple hair, red eyes and is wearing a black and purple bodysuit, in her right hand was a red spear. These are Jeanne D'Arc, Sherlock Holmes and Scathach.

"They're strong…" Scathach smiled. As she stabs her spear to another skeletal soldier.

"I agree…" Jeanne nodded swinging her flag causing winds through the enemies with Sherlock using his cane bash destroy them all at once.

"Well, this is getting annoying." Sherlock calmly said.

However, another group of minions suddenly tries to ambush them, only to be gunned down by James Moriarty as well as being slashed by Arcueid. Ritsuka then called out, "DA VINCI! EVERYONE! YOU ALL RIGHT!"

"We're okay, Fujimaru." Sion answered.

Ritsuka then asks Rider Da Vinci, "Da Vinci what's happen?"

Rider Da Vinci sighs as she replied, "To tell you the truth, we have no idea. But if I have to guess it's got something to do with what's happening outside…" This caused Ritsuka's group to be shocked, with Arcueid then asking.

"Can I ask you something…"

Sion narrowed her eyes as she replied, "Yes what is it?"

"Do you see someone leading the attack?"

Jeanne then replied, "Yes… And that individual sounds like she's related to Zelretch." This caused Ritsuka's group especially Arcueid to be shocked.

"What do you mean?"

"Well—"

A few minutes Ago, inside the Storm Border, Antarctica

2023 AD

We then go back a few minutes, where we saw that the entire people of Chaldea are minding their own business. With Sion, Da Vinci, Sherlock and Goredolf walking down the hallways.

"My it's a beautiful day isn't it…" Goredolf smiled.

Da Vinci giggled, "Well It is obviously after all that we went through, the least we can do is relax."

Holmes nodded in agreement, "On that we agree…"

As they continue to walk Sion asks Rider Da Vinci," By the way where is the other you, Da Vinci?"

"Well, She is currently on our workshop working on some things…" Rider Da Vinci replied.

As they continue to walk, Rider Da Vinci as well as most of the Servants sense something is amiss. With Holmes saying, "Did you all feel that?"

"Yeah, we do…" Rider Da Vinci replied she then called out, "COME ON OUT! WE KNOW YOU HAVE BEEN PEEKING ON US!"

Suddenly, they hear a female voice saying, "My, looks like my cover's been blown… Seems like Zelretch's student has a lot of impressive friends." They turn and saw a cloaked figure holding a staff with a crescent moon.

"Wait, who are you? And how did you know that name?!" Holmes demanded.

The Cloaked figure smiled as if she finds it amusing, "You're a detective, aren't you? Why don't you figure it out." She snarked at Holmes.

"What are you saying?" Sion and Goredolf asked.

The cloaked figure smirked, "Oh you will find out, but first let me rain hell on this place!" She shouted as she summons the minions who then each stand up as she shouted, "KILL THEM ALL!"

The minions nodded as they started to charge towards them, when suddenly another voice shouted, "We won't let you!" Two flashes of blue and purple suddenly destroy them. They saw that it was Jeanne and Scathach.

The two looked towards Sion's group with Jeanne asking, Are you all alright?"

"Yeah, we are!" Rider Da Vinci answered.

She and Scathach pointed their weapons at the cloaked figure demanding, "Who are you? What is your purpose!?"

"Oh nothing… Just look at the sky…" The Cloaked figure she pointed at the window, Sion's group looked at the direction of that the figure was pointed at and were surprised at what is happening outside. They saw the as red as crimson with cracks forming. With portals appearing occasionally.

"What is going on?" Jeanne D'Arc muttered.

Rider Da Vinci said, "The Sky…" She then glared at the cloaked woman, "Was this your doing?"

"Who knows… although my back up is here so tata! Oh, and tell the Master of Chaldea and the Moon Princess that the Brotherhood is coming." The cloak woman disappears with Jeanne and Scathach.

"Damnit, she got away!" Scathach mumbled angrily.

We need to go to the control room now!" Sion stated.

As they ran, they heard a loud boom, they turn saw that another horde of minions are now rushing towards them, "I think we have company." Goredolf said shakingly.

Present, Inside the Storm Border, Antarctica

2023 AD

We then cut back to the present day, with Ritsuka saying, "I see so that's what happened…"

"Yeah… and that's the whole story." Sion answered,

However, as this was going on, Holmes looks and notices Arcueid who was now looking very sweaty, "Mrs. Brunestud… what's wrong?"

"Did you just say, the Brotherhood?!"

"Yeah why? Did you have something that could help us?!" Scathach inquired.

Arcueid looks at Ritsuka who looks at her with a nodded, She then proceeds to tell Sion's group about how Zelretch and Aoko are being chased with Sion's group widening their eyes, "Now after what we have heard from you Sion… I believe that the Brotherhood were the ones chasing the two."

"What makes you so sure about that? And what is this Brotherhood anyway?" Dantes asks the princess.

Arcueid looks at them as if to she was reluctant to answer, she then inhales and exhales, She then explains, "Yes, I'm sure, And as for the Brotherhood. They were a group of Mages that like Zelretch specialize in traveling parallel worlds. But they took it a step further by going to other dimensions."

This caused the others to be shocked with Rider Da Vinci muttering ass he fuddles with the computer, "So that's the reason those cracks are appearing…"

"It's there overuse of their powers, and I have to guess they need Zelretch and Aoko to stabilize it." Holmes stated.

Whilst Rider Da Vinci as analyzing the cracks and the red sky. They heard a call from the Association, "Oh boy…"

They turn on the call and saw that it was none other than an Auburn woman with white clothing this is Barthomeloi Lorelei who then shouted, "Ritsuka Fujimaru! What is going on now?!"

"Umm…"

" Lorelei-sama we can explain but first you need to top yelling." Mash said.

"Okay..." Lorelei inhale and exhaled, "What is happening we are getting reports of the sky going red, cracks opening and what is this about Zelretch and Aoko missing? Can you fill me in on what's going on."

They then explain to Lorelei about what happened, and who are the mastermind, this caused Lorelei to darken her expression, "The Brotherhood I haven't heard that name in a long time."

"So, you knew them?!" Ritsuka asked.

"Knew them? Me and the other Lords were the ones who exile them. due to their Magecraft being deemed too dangerous!"

Ritsuka sighs, "Calm down Lorelei! Calm down!"

"So, what are we going to do about this?" Lorelei asked.

Rider Da Vinci completed her analysis and saw something interesting, "Everyone look at this."

"What is it, Da Vinci-chan?"

"I've analyzed the cracks in the sky, and I've discovered that these cracks were portals to other dimensions. And it has some traces of the Third Magic in it."

"Then that means—" Mash said.

"Yes… it means that we can theoretically travel through it, but it might give the Storm Border some serious damages." Rider Da Vinci explained she then said, "At this point we will call the dimensions over there as 'Parallel-Singularitiesl'."

However, Lorelei is now losing her patience, "I DON'T CARE IF IT'S DANGEROUS! RITSUKA FUJIMARU, I WANT YOU AND CHALDEA TO EMBARK ON THIS MISSION NOW!"

"But—"

"NO BUTS! JUST DO IT!"

The Chaldeans just sighs as Lorelei turned off her transmission, Arcueid sighs, "Looks like we're going on another adventure huh?" She then looks at the others "So, you guys ready?"

"Yeah, but first let's call everyone…"

3rd POV

A few hours later, inside the Storm Border, Antarctica

2023 AD

We then cut to a few hours later, and we saw the Chaldeans alongside a new addition which was a young boy with ashen blonde hair, blue eyes and wearing white Indian clothes, this is Captain Nemo.

"Man, this is a hassle."

Sion then patted Nemo saying, "Don't be like that it's been too long since we last go on an adventure together."

Nemo sighed, "Looks like my work is never done, okay everyone you ready!"

"Yeah, we're ready…" Ritsuka said.

"Okay then…" Nemo then saw a crack forming in the sky, he smiles, "All Triton engines activate." The thrusters of the border activate as it started to fly, "Ok… Everyone let's get ready for another adventure! This is our next Grand Order called 'Parallel Order' everyone!"

The Storm Border then went to the crack as it tries to enter it. With it sustaining a few damages before it enters it. As the cracks disappears.

In an Unknown Universe, in the skies of New York

2020 AD

"You Ok, Senpai?" Mash asked.

"Yes, yes I'm okay, Mash." Ritsuka replied. As soon as the Storm Border reaches the end of the portal, as soon as the view cleared, they were now in a what appears to be the skies of New York.

"My. Never would have thought we'd be in America of all places." Galahad muttered.

"Well, here we are…" A woman that looks like an older version of Rider Da Vinci said. This is Leonardo Da Vinci (Caster), "The First Parallel-Singularity…"

Mt. Olympus, Empire State Building, New York

2020 AD

We then cut to a Greco-Roman-themed hallway filled with thrones sitting are large men and women wearing modern and Greco-Roman clothing, As they sit one of them said, "Everyone do you feel that?!"

"Yeah, it is as if we are looking at a mirror, "The bearded man in the center said.

The grey-eyed woman then inquired, "You sure about Zeus?!"

"Yes, I'm sure…"

Meanwhile, Inside the Realm of the Dead, Duat

2020 AD

Meanwhile, we saw a 14 year old brown bald pony tailed man wearing a leather armor with a sickle sword in his side, a blue skinned man wearing pharaoh's clothing, a fiery sand man with red eyes.

"Horus do you feel that?"

"Yes, this feeling it feels similar to my host Nitocris…"

"But that's impossible she should be dead a long time ago!" The Blue man said.

The Sand Man then interjects, "Not only that… I also felt Ramses just now…"

"Seriously, Ramses too?"

"What in the world is going on?"

Elsewhere in Asgard, Nine worlds, Yggdrasil

2020 AD

As this was going on, an eyepatch grey haired man was sitting on a throne as two crows were sitting in his shoulders. He then open his eyes as he muttered, "Looks like we have some unexpected visitors."

He then stands up and he muttered, "Looks like I need to see Magnus again…"

On an unknown Location

2020 AD

A bunch of cloak men are now sitting in chairs with the center saying, "Looks like Chaldea has followed us here after all."

The one at the right giggled, "Wow that's fast…"

"Well, I expected as much from Zelretch's associates, especially the Moon Princess." One of them muttered.

"Well guys let's go back to our respective dimensions wouldn't want to keep our 'allies' waiting…"

"Yeah…"

They then disappear leaving the one with two short swords and a staff, "Looks like works never one, huh?"

Author's Notes:

Now that's for the prologue… I have been writing this without an outline so, expect that there are changes okay… Especially now that Ordeal Call is coming.