Angra Mainyu caught up to Shirou but didn't kill him. Instead, she laughed and said, "I'm going to remake this world. As the victor of the Holy Grail War, I'll give you a way out. Leave Fuyuki and I'll spare you."
"What about Scathach?" Shirou asked.
"She'll become fertilizer to remake the world," Angra Mainyu said with a laugh. She then headed towards the Einzbern Castle where black mud poured down.
The place had become overtaken by the black mud.
Shirou didn't panic. As someone convinced this was all just a bizarre dream, how could he?
It was just...
"Is the exit from this dream at that black mud?" He wondered.
He figured it couldn't hurt to give it a shot. Even though he had no idea who had created this dream world, things had progressed to this point. So the mastermind would probably reveal himself soon.
More importantly, Scathach had been captured by Angra Mainyu.
No need to elaborate on Shirou's complicated feelings about Scathach. The main thing was, even as his 6-year-old self during the 4th Holy Grail War, he definitely wouldn't just stand by and do nothing to help her.
Shirou knew full well what kind of person he was. He never denied that he could be sneaky and underhanded, whether before or after his awakening. But at the same time, he also understood his own character.
He was the type to remember debts. If people wronged him, he'd make a note of it and get revenge later. But if people helped him out, he'd remember to return the favor when he could. An eye for an eye, and a kindness for a kindness.
Although this version of Scathach wasn't her main body, the will attached to the Servant was still her own. So even without having awakened yet, there was no way he'd stand by and let Scathach become fertilizer for Angra Mainyu.
However, Angra Mainyu's sudden appearance had caught him completely off guard. His notebook had no helpful information on dealing with this situation either. He'd have to figure out the next steps on his own.
The problem was, he currently had no power whatsoever - not even EMIYA's Saint Graph that he'd obtained earlier in the Grail War. How could he possibly take Scathach back from Angra Mainyu's hands? Would he have to acknowledge [All the World's Evil] and inherit it again? He didn't take much time to think it over before heading straight for the Castle.
Einzbern Castle was located on the outskirts, surrounded by a thick, old forest filled with towering trees. However, in the version of Fuyuki City that Shirou had stayed in before, the castle was gone - replaced by an industrial park.
Yet in this dream, he found himself in the Fuyuki City of the 4th Holy Grail War. So the Einzbern Castle should still be there. But when he went to the outskirts, he saw that was no longer the case.
The sky had a massive hole torn open, with black mud pouring out like a waterfall and spilling to the earth below.
"Hiss, hiss, hiss..."
Fires blazed where the mud touched the ground.
The towering trees surrounding Einzbern Castle fell one after another. The old trunks, which had stood for hundreds of years, were no match for the destructive disaster.
Shirou walked toward the castle, the command spell on the back of his hand - his last connection to Scathach - guiding him like a beacon.
On the road to Einzbern, black mud surged wildly. This was not the mud guarding his main body back in reality; this was a vile, cursed mud that sought to destroy everything - including him.
Shirou did his best to dodge the deadly tide, but in this dream, he was just an ordinary boy. Soon a spatter of mud seared his arm.
"Hiss hiss hiss--"
The skin on his arm instantly burned away, hissing from the contact.
The pain was intense, but nothing like having his whole body incinerated by Ea. He had survived worse.
Gritting his teeth, Shirou kept moving, carefully skirting around the black mud.
But no matter how cautious he tried to be, his six-year-old body just wasn't agile enough. More black mud splashed over him as he went, searing agonizing wounds across his flesh.
Shirou slipped through the front gates of Einzbern Castle with a creak. The moment he stepped inside, the space warped around him, replaced by the interior of the castle.
Black mud oozed through every room, devouring everything like a swarm of ravenous locusts. The black mud was consuming the castle from the inside out.
He scanned his surroundings until his eyes landed on a nearby window. Two Einzbern maids who had already been captured by the black mud writhed there. The mud had consumed their uniforms, revealing their fair skin underneath.
But there was nothing alluring about the sight - the black mud clung to their bodies like locusts, gnawing away at their flesh.
With a sickening thud, one maid's arm detached from her body and fell to the ground, only to soon be swallowed and consumed by the black mud.
It was devouring their flesh, muscles...even bones.
A horrifying, gruesome sight.
This was the true nature of All the World's Evil.
It was not the black mud acknowledged by Shirou and imprinted with his psyche, but rather absolute evil in its purest form.
Destruction, curses, hatred... It represented calamity strong enough to destroy everything!
Rather than saying the black mud was harmless, it would be better to say that because the usual black mud had assimilated into Shirou's psyche, it had become harmless. [All the World's Evil] was not harmless, Shirou was.
"How interesting. I'm quite surprised you actually came here."
A somewhat surprised female voice rang out near his ear. Shirou turned his head slightly and looked toward the main hall. At some point, a throne formed of the black mud had materialized there, and Angra Mainyu wearing Irisviel's body sat upon it, watching him mockingly like a Queen.
"I've come, Angra Mainyu. Where is Scathach?"
She smiled, "Isn't she right under your feet?"
Hearing this, he lowered his gaze slightly, only to find the marble floor already covered by black mud without him noticing - pitch black and crystal clear, like obsidian.
And in the layers below this mud, bodies wrapped by it were frozen one by one. Diarmuid, Spartacus, Artoria Pendragon...as well as Scáthach. Even Iskandar and Gilgamesh weren't spared, trapped within.
Shirou looked back up at Angra Mainyu and asked, "Are you going to alter them?"
"Alter? Hahaha..." Angra Mainyu, seated on the throne, seemed to mock him with laughter. "I'm surprised you actually know this function of the mud. As expected from the victor of the Holy Grail War."
Shirou thought to himself, of course I know, because I'm also using the black mud.
"I had this plan before, but one Heroic Spirit has a very strong sense of self," she smiled, "If I did that, it might have backfired on me instead, so I gave up. Besides, since I've already materialized, why would I still need to use them?"
Shirou knew who she was talking about - it was Gilgamesh.
Looking at all the confined Heroic Spirits again, he realized that apart from Scáthach, all the other Heroic Spirits were in spiritual form. That made sense, of course. After all, in this dream, all the Heroic Spirits had been killed by him and Scathach.
"However, I'm quite surprised. From my understanding, you should be a coward, yet you dare to come here. This really surprises me."
"Of course I'm very afraid of death, but sometimes, even if you're afraid, you still have to do what needs to be done."
"Lies," she responded dismissively.
He spread out his hands, "If you don't believe me, you're welcome to look into my mind."
"Why would I do something so pointless?"
He laughed, "I killed Kiritsugu and tied up Irisviel here, so she's full of hatred towards me. And you're taking over her body to manifest by using her hatred. So of course, you'd also hate me and want to kill me. Even if I don't say it, you'd still enter my mind and trample my soul. Right?"
The smile on her face faded. She narrowed her eyes for a moment, examining him, "I have to admit, there's a reason you won this Holy Grail War. Yes, even if you don't say it, I will still trample on your soul. By the way, even if you hadn't come here, I would have killed you. This is my hatred, Irisviel's hatred towards you!"