Deep beneath the Ryuudou Temple, in a vast cavern laid the Greater Grail. It was not an actual grail, no that was the job of the Lesser Grail, a key that would activate the Greater Grail. The Greater Grail was a massive and intricate magic circle that would serve as a gateway to the Root once the Lesser Grail gained enough magical energy from the Servants it summoned.

However, the Holy Grail was not as 'Holy' as its name would suggest.

The Einzberns had grown desperate in their quest to reclaim the Third Magic, the ability to manifest souls. They soon realized that they would never be able to regain it by themselves so they enlisted the help of the Matou and Tohsaka families to construct the Heaven's Feel ritual, which would be known as the Holy Grail War. Unable to win the 2 previous Grail War, by the 3rd Grail War they decided to summon an Anti-Hero servant rather than a True Heroic Spirit.

Angra Mainyu, All The World's Evil

The Einzberns believed that by summoning the manifestation of all the evil in the world, they would be able to win the War through brute force. However, Angra Mainyu was not the deity they had originally believed him to be as he was just a simple man that was decided by his village to hold all of their sins and be sacrificed so that they would be freed from them. As a result, he was so soundlessly crushed by the other servants that the Einzberns were the first to be eliminated from the 3rd Grail War

But for Angra Mainyu, his story did not end there.

As he was absorbed into the Grail so too was the curses that he seemingly absorbed from his village. The once blank canvas of the Holy Grail War was now tainted with the corruption of Angra Mainyu, allowing the summoning of Anti-Heroes such as Gilles de Rais. Such a tainted grail could be now considered a true manifestation of the World's Evil.

However, as Caster gazed on its tainted state, all he could feel was disappointment.

This was the World's Evil? He expected something a bit more sinister. Maybe some kind of demon capable of destroying entire realities that it would have to the Grand Servants to stop, a Beast of Humanity almost. Yet this was all that was here in this cavern? A wish-granting system that was corrupt, had Angra try to make an attempt to grow stronger, to maybe hijack the Grail and use its power to fully manifest to what the Einzberns had wanted him to be then maybe he wouldn't feel the need to kill him. He was almost wanted to spare him and let him accumulate power from the upcoming grail war but that would've screwed his plan over so he felt no remorse of what was to come next.

"Alright time to die Angra." Placing a foot in the cavern, Caster was ready to obliterate the Avenger servant.

He did have to applaud Angra for his efforts however. The moment he had stepped foot a barrage of corruption tendrils shot out from the magic circle. Shooting forward like missiles, the tendrils hoped to damage the Great One that had stepped foot in its domain; hoping to kill and corrupt him. Any lesser servant would've instantly faltered against such a barrage, unable to defend from the endless number of tendrils.

But for Caster, they were just as easy to swat like one would do with a fly.

Letting out some of his magic, in a bright flash any approaching tendrils had been eradicated. However, this did not deter Angra as he continued to launch more tendrils at him. With each hundreds of tendrils that Angra launched, Caster released a miniature supernova that would render Angra's offensive useless until he was in the middle of the magic circle. By this point Angra had activated what little energy that the Greater Grail had accumalted over the years to try and preserve his life. From hundreds to thousands the tendrils now looked like a blanket of corruption that tried to envelop Caster.

"Alright now this is getting annoying." Whipping out a hilt, Caster muttered a few incantations in the tongue of the Great Ones. Realizing that what he was about to do Angra begun to put any vestiges of energy left within the Greater Grail had left, not caring that he might die in his attempt. Finishing his incantation, Caster allowed the hilt to take cosmic energy into the form of a sword, humming with the tune of the galaxies. With one slash of his sword any hope that Angra had of survival was taken away as the resulting blast wiped out any present corruption within the Greater Grail.

Losing all hopes of trying to fight back, Angra Mainyu was left to the mercy of Caster. "Don't get the wrong idea from this Angra but I really sympathize with you, I am not without benevolence. I know what that village did to you in their attempt to cleanse their sins. All that torturing and beating turned you into the horrid thing that you are today." Reaching down, Caster allowed his hand to break through reality itself to enter the inner workings of the Greater Grail. He had to give credit to the 3 Founding Families for the care and intricacy that went into building the Heaven's Feel.

Locating the last vestiges of Angra Mainyu, Caster grabbed the corruption parasite. Feeling the parasite wiggle around in his grasp, he gave his final farewell. "This is goodbye Angra Mainyu, may wherever you end up treat you far nicer than this place has," and crushed the parasite with cosmic energy.

And thus Angra Mainyu alongside the corruption he had inflicted on the Grail disappeared.

Pocketing the now sword less hilt, Caster gazed up at the ceiling of the cavern. Night had descended over Fuyuki City and so too would the Holy Grail War begin. As the moon took its place over the night, so did he feel his control over the city take hold. Across the city he could feel his Noble Phantasm take its hold on the city. Careful ritual preparations during the 1st month had allowed his Noble Phantasm to take hold without anyone noticing.

Smirking he could feel the 6 other servants converging by Mion River, preparing to show themselves for the others to see. Chuckling Caster went into spiritual form to prepare his grand entrance

After all.

What kind of host would he be if he didn't personally introduce the servants and masters into the nightmare they were walking into.

"Maiya is Assassin still there?"

"Affirmative, he still has yet to move."

"Keep watch till he moves."

"Affirmative Kiritsugu."

By the docks of the Mion River, the first battle of the 4th Holy Grail War had begun. Saber had been called forth by a challenge by Lancer. Challenged in the name of Chivalry, the two clashed in a battle worthy of legend. Even for Kiritsugu, the Magus Killer, it was hard to track the movements of both knights as each clash would shake the ground. While having Saber being King Arthur, Revered ruler of Camelot, as an opponent; Lancer, Diarmuid Ua Duibhne, was worthy enough to be considered her equal in this battle of skill. Both were equally matched with Saber's skill using Excalibur and Diarmuid's prowess with his dual spears. However, such a stalemate between servants would not last forever. It was Saber who made the first folly as she severely underestimated the power behind Lancer's spears.

Now she had a wound on her left arm that would not heal, courtesy of Gae Buidhe, The Golden Rose of Mortality in which the wounds that it inflicted would not heal so long as the spear existed. Having his identity revealed meant that the other spear was Gae Dearg, The Crimson Rose of Exorcism which pierced through any magical defenses. Having Noble Phantasms that rendered any defense that Saber possessed useless; he was about to step in to stop the fight before it got any worse, by shooting down Lancer's master.

That is until Rider rode in on a blaze of glory.

Declaring his true name for all to hear, Rider had effectively stopped the fight as both Saber and Lancer gaped at his casual reveal of his true name, his master included. A servant's true name was in essence their weaknesses laid out in front of you. Knowing a servant's true name allowed one to gleam their legend, to be able to know what their strengths and weaknesses were. Yet for all that a True name entailed, Kiritsugu could tell that Iskandar had taken that disadvantage and flipped it to become an advantage. A normal master and servant would regard Iskandar as a fool and proceed to take him lightly when it came to exchanging blows. That disregard would lead to one underestimating the might of The King of Conquerors. After all, he did not conquer Macedonia with brute strength alone.

Having had his invitations to join his army shot down; Rider called forth the other servants that had been watching in the shadows but chose not to act.

The first to respond had been the Golden Archer, the one who seemingly decimated Assassin.

Just from a glance he could tell that Archer would be the strongest servant in this Grail War. The way he had established himself above the servants it was obvious that he was the arrogant bunch. Though unlike most arrogant people he had the displeasure of knowing, this Archer had the power to back it up. When Archer called forth his projectiles through his golden portals, one could tell that they were Noble Phantasms.

Then Berserker showed up, the Black Knight howling in madness.

6 different servants, excluding the Caster Class which had yet to show themselves, had showed up and the tension between them couldn't be any more obvious. Each servant had their own reason to fight for the Grail and with all of their opposition sitting right in front of them, all it would take was one tiny action to ignite this bomb of legends into chaos. "Maiya has Assassin moved?"

"Negative Kiritsugu, Assassin has yet to move." Swiveling his gun to where Assassin had perched themselves before the appearance of the other servants, he was able to confirm that Assassin had yet to move. Cursing on how fast the situation was unraveling before their eyes, he gave some orders. "Maiya continue observing Assassin, there's no way that they wouldn't act at a time like this." After giving her orders, he continued watching the situation with the servants.

"Who gave you permission to look upon my form?" The Golden Archer addressed Berserker who was looking at him with intrigue. How dare this mongrel gaze upon his perfect form without his permission. Summoning his gates, he brought forth two weapons to which he pointed at the crazed knight. "May your death bring me some form of entertainment mongrel!" and he let the 2 Noble Phantasms fly at Berserker.

This was getting out hand before long all servants present would be fighting with each other. The devastation that they would leave in their wake would be too much for even the Church to cover up. In addition, Irisviel would also be in harm's way if it did dissolve into that mess scenario.

It seems that his unspoken prayer for the fighting to stop had been answered, but he would soon realize that he'd rather take it back.

From the night sky, two bullets of cosmic energy raced across the sky before colliding with the swords of Archer, creating an explosion. Having had his judgement stopped Archer glared at the sky where the attack had come from. "Which unruly mongrel dares to stop my judgement!?"

"Oh? And who are you to assume that you are my better Archer?" Descending from the night, on butterfly wings formed by cosmic energy that radiated authority, Caster smirked as all attention was put on him.

"It appears that introductions are needed. I am Caster," Bowing Caster let a bit of his authority shine as his once normal eyes became a swirling galaxy of power.

"Sorry for being late."

Caster grinned as the tension seemingly became directed at him, and for good reason. Here was a servant who belonged to class that would've never introduced themselves to other servants and most certainly not stop an attack from the what was supposedly the strongest servant in the Grail War. He would be changing that perspective very soon.

"Oh, it seems that all Servants are accounted for." Leave it to Iskandar to break through the tension. Bowing his head to Rider, Caster agreed with his statement. "It was your statement that moved me to reveal myself oh King of Conquerors. "

"Then you must know what I am about to ask you next."

Chuckling Caster would play his game. "Apologies Rider but I am uninterested in joining your army, the conquest of the world does not interest me."

"But you are not opposed to it?"

Laughing at how Iskandar so easily deflected his answer back him, he allowed him to have this battle of wits. "If I ever feel the need to conquer the world then I shall join you."

"Very well Caster; still out of all the 7 servants, one is dead before I can even ask to join my army and another who is not opposed to the idea." Grinning wildly Rider raised his arms. "It makes me want to try so much harder to convince all of you to join my army even more now."

Waver was ready to kill himself right about now. Not only did Rider charge into a match between Saber and Lancer, he revealed his True Name for all to hear, his previous teacher knew he was here and he would probably suffer because he had the gall to steal his relic. Now he had to deal with his servant trying to recruit other servants. Why didn't he just stay at the Clocktower?

"Oh? Are we talking about Assassin? Why don't we ask him ourselves" Caster chimed in.

"Impossible! Assassin died on the first night," Kayneth argued from his perch on top of the warehouse.

"Master of Lancer, why should I heed the words of a rat that hides in the darkness when all others have shown their face." Looking down on Lancer he decided to twist the knife in Kayneth's pride. "This is the slimy magus you have pledged your loyalty to Lancer?" Without any reasoning to defend his lord, all Lancer could do was avert his face in shame. "And who are you to assume my logic is wrong, I am of the Caster class, such poorly designed schemes cannot hide from my insight."

"Then what did we see?" Waver asked curiously.

"A usage of Assassin's Noble Phantasm, normally I would never share such info about a servant but seeing how they have yet to show their face to us," Pausing a bit Caster projected his voice. "Assassin there is no point in hiding, we know you are here, come out would you."

And yet.

Assassin, still believing that they were safe, chose not to reveal themselves.

Sighing Caster apologized what he was about to do next. "Very well, I feel no remorse for what will happen next," and snapped his fingers. Then a loud demonic screech filled the air. The last thing that Assassin, or rather one of the personas, experienced was suddenly being dragged from their perch and slammed down to the ground, a large demonic beast looming above them before they died.

"What was that?" Saber asked as she positioned herself in front of Irisiviel, ready to defend her at any moment.

"Oh, nothing much, just my pet taking care of some loose ends." Vanishing into spirit form Caster gave some last remarks. "Welp I'm off but I'll leave my pet here as a taste of what is to come, don't die on me yet!" And with that Caster left the scene.

And then his 'pet' entered the scene.

Approaching from an array of containers, the beast looked at the gathered servants with interest. This was a Cleric Beast, a once revered member of the Healing Church that had turned into this unsightly beast. Those of the Healing Church were the ones that turned to the most hideous of beasts. The enormous wolf beast with its disfigured horns stalked forward with its prey in hand.

Assassin, or what was left of this copy, could only be dragged by the imposing beast. It was so easily crushed that it should've have departed for the Throne by now, which did not happen. The only it could do was allow the beast to drag its corpse around, smearing the ground with their blood.

Before anyone could react, the Cleric Beast roared once more into the night before engaging the servants.

There the servants would get a taste of the hunt that they would find themselves in.

And while all this was happening, without anyone noticing, the once innocent moon had begun to turn red, a beginning to the bloody night that would soon begin.