(Disclaimer, this is not connected to my other fan fiction Fate Merveille. This is a separate story completely using the Ladybug and FGO characters with my oc, Kirsi Cereza.)
The sky turned a dark grey and the air turned cold. Paris was being consumed by an ice-cold winter. Marinette and her kwami Tiki looked out the window, snow started to fall in the middle of summer. But that wasn't the only thing to confuse the two, a bright light in the sky shone with a deep red tone. Sparkles seemed to surround it and circle it like planets to a sun. Marinette opened the door and transformed into the superhero Ladybug with the ice powerup. She jumped outside to meet Chat Noir. The two had no idea how they would reach the light, so went to their master, Wang Fu, for help. Master Fu only told the heroes to take care of the people of Paris, for they didn't have the ability to reach a structure suspended so high in the air.
"What do you think milady?" Chat Noir looked to Ladybug for her thoughts.
"Whatever it is, it's going to be hard to take down," Ladybug said.
"Do you think it's an Akuma?"
"If it was, it would have attacked us by now."
The supervillain Hawk Moth and his partner Nathalie stood in a room that overlooked Paris, the entire city was filled with fear and confusion, a perfect time to enact his plan once again. With the help of Catalyst, he spread his many akumas far and wide, turning most of Paris into supervillains. That surprised Ladybug and Chat Noir, the two were overwhelmed with constant attack and had no way to contact Master Fu to recruit their allies. Suddenly an arrow made of electricity pierced through a jacket and released the akum from it. Ladybug purified it and looked to where the arrow came from. A man with dark hair, brown eyes, a white suit and held a bow with an arrow ready stood before her. Another from behind ran and struck right where an akuma was hidden. The second man wore armor that concealed his dark blue attire and his blonde hair was only visible while his face was covered.
There were others who stood by the man with the bow, a girl with fox like ears and a tail, another girl with a flashy red dress, a man with dark hair except for some parts where it was white, and a fighter with pink hair in a braid who rode on a hippogriff.
"Looks like you got yourself in some trouble," the man with the bow said to Ladybug. "Mind if we help out?"
"Who are you?" Ladybug asked him.
"I am Arjuna, and these are my friends."
"More fight, less talk!" The fighter with the pink hair yelled out.
One by one, each super villain was defeated with ease. The new superheroes knew exactly where to strike and were careful not to be attacked themselves. When it was over, Arjuna properly introduced himself and his team. Arthur Pendragon, Tamamo No Mae, Nero Claudius, Charlemagne and Astolfo. They were all brought to Paris by the appearance of the structure in the sky. Their plan was to infiltrate it and take it down, they asked for Ladybug and Chat Noir's help, but the two superheroes weren't sure what to do. On their own they couldn't defeat such a thing, however, with the help of the new heroes, they had a chance.
"Hold on milady," Chat Noir whispered to Ladybug as he pulled her aside. "How do we know they haven't been akumatized by Hawk Moth and are pretending to help us?"
"I know, I know, we'll just have to be careful."
"Do you think it's him?" Astolfo asked Arjuna, which was overheard by the two.
"It has to be," Arjuna responded.
"Will you be okay fighting him again?" Nero asked another question.
"I have to, the battle in India was only the start, we have to stop him here."
"This isn't exactly the greatest place to fight, too many buildings," Charlemagne pointed out.
"We destroyed the Grail to halt his plans, we can't let him have the power that lays in Paris. We won't have this chance again." Arjuna then looked at the two superheroes to see they had been listening in. "I apologize, we'll need a place to sit down and talk about this properly."
Master Fu appeared and offered his home as a place to hear out what Arjuna had to say. He kept his identity as the guardian of the miraculous a secret just in case Arjuna was working for Hawk Moth. Arjuna sat down with the rest of his team in Master Fu's house while Nero held tightly onto Charlemagne's arm to keep him from touching anything and breaking it. Arjuna explained the basics of what they were planning; there was someone they were tracking down and had to stop, the person wanted to rewrite history with the power of the miraculous. Having doubts in his new allies, Arjuna kept the person's identity a secret.
Tamamo No Mae continued the explanation, their journey started in India, where a power was discovered. Their ally turned enemy was corrupted by the Grail and they were forced to fight. Their team was split between Arjuna and their former ally, with one of their masters going to the other side. A powerful mage capable of creating storms, just like the one Paris was suffering from. Charlemagne ended with telling the superheroes that the group were forced to destroy the Grail then followed the structure in the sky to Paris. There were rumors about a power that could grant wishes, much like the Grail, and their former ally wanted that power.
The structure in the sky, a floating castle, holding the ones who sought a special power for their leader.
"Are you sure it's here?" A woman with a pirate like attire asked.
"Why question it?" A girl with horns and a dragon tail snickered. "The master knows what he's doing."
"Even so," a woman holding a flag interrupted. "How are we to find this object master seeks?"
"If it truly exists," a man with full golden armor on a golden throne said. "We will find it."
"Are you all still bickering?" A girl entered the room. She had brown hair in a bun, dark blue eyes, and wore a purple Indian dress with golden earrings.
"Sorry," the pirate apologized. "We're just wondering if the thing master seeks is here."
"It is, we just have to find it." The mage girl summoned her black staff and pulled black feathers from it. She opened the window and blew them into the clouds. "We will find it and rewrite the past."
"Initializing, Chaldea staff, this is Leonardo da Vinci. Do you read me?"
"I can hear you," Fujimaru reported. "It's so cold here, are you sure it's summer?"
"It is, I'm sending you information on the current state of the Lostbelt. Be careful Fujimaru."
"Let's go Mash."
"Yes senpai!" Mash trailed behind her master to the cold city of Paris.
(So, I'm a dumb and got Arjuna's eye color wrong. They're brown in his regular form and blue in his alter form.)