Muzan Kibutsuji was standing outside a large building. The no longer emaciated Moon Zero stood behind him. They were meeting the strange man in the screen here, but they didn't know what he wanted. At any rate, Muzan didn't feel threatened by him
The door opened. Muzan told Moon Zero to wait there. He walked into the building. He saw strange vats with odd creatures inside them submerged in a liquid with hoses attached. He lingered on three of the creatures as he continued walking through the building. He could feel the power within them. But something about them felt off. The third one he lingered on he just stayed at.
"Magnificent, aren't they?" He heard echo through the building.
He turned his head to where the voice originated. The man from the screen sat with an eerie smile plastered on his almost completely featureless face. Muzan turned away from him and turned his attention back to the creature.
"These are some of my own creations. Well, a mix of mine and a good associate of mine. Beings fused with multiple Quirks. Conditioned to obey orders. Some are tough enough to fight All Might in his prime. My second most prized possessions. My Nomu," the man said.
"Artificially created beings infused with power. Your second most prized possessions? Then which is your most prized: Tomura Shigaraki or Kurogiri?" Muzan asked.
"Both of them are tools. One of which I plan to use to obtain what is my true prized possession: One For All."
"You do not own this One For All? Then how is it your prized possession?"
"It belongs to me. It is vital for my plans of world domination. It is something I unintentionally created. If I created it, it is mine."
"How could you accidentally make something that you so dearly want and lose it?"
"My dear little brother was thought Quirkless. I gifted him a power stockpiling Quirk to give him power and a reason to stand by my side. But he had a useless quirk that allowed him to pass his quirk to others. The two combined and have been a force trying to stop me ever since."
"I should think the solution obvious. Kill whoever holds One For All and continue with your pathetic plans for domination."
The man stood up at that statement and walked towards Muzan with his medical equipment following. He towered over Muzan, but even then, Muzan wasn't intimidated.
"You would do well to remember who you serve, Muzan," he said.
Muzan looked at him with contempt. Yes, this man was powerful, but he was The Great Demon Progenitor. Any attack he would take he could heal from, no matter how grievous it may look. This man? His upper face was scarred, he didn't even have eyes, he just looked like a featureless doll with melted head. But he was strong. The only thing was he didn't know how strong.
"And yet you have yet to tell me who you even are," he said.
"I am All For One. The Symbol of Evil in Japan. The Great Demon Lord," the man said.
That title, Great Demon Lord, that got under Muzan's skin easily. As the progenitor of all demonkind, he was the Great Demon Lord, not some almost literally faceless brute. If Muzan knew the full range of powers of All For One, he would have killed him then and there. But he might have a quirk that could allow him to bypass the Sun or kill him. He would have to know the extent of his power.
"What's to stop me from going to the police of this time, telling them where you are? What you're doing here?" Muzan asked.
All For One scoffed. A screen floated over to them. In it was a human, battered and bloody. His eyes were filled with fear.

KAMU SEDANG MEMBACA
Slayers And Heroes
Fiksi PenggemarA hidden demon. A Demon with powers that rival his master's. A Demon with control over time and space. A Demon known as Moon Zero. More powerful than the Upper Moons. Older than Kokushibo. This demon was never near death. Until one day, after the as...