What is the Infinity Fortress in Demon Slayer?

Demon Slayer: Infinity Fortress is getting a lot of attention from fans. So what's inside Demon Slayer's Infinity Fortress ? Let's find out together!

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What is Demon Slayer: Infinity Fortress?

Have you ever seen those MC Escher fantasy art pieces? Specifically the one called "Relativity" with the stairs on the wall and people walking upside down but in the right direction. Imagine that but the Infinity Castle is a thousand times more confusing and has more rooms. The main base of operations for Twelve Kizuki and Muzan as well as the setting for the finale of Demon Slayer, the Infinity Castle is like a giant subspace filled with rooms, stairs, balconies, and hallways. This giant fortress can appear anywhere, at any time, and transport its occupants wherever they want. Muzan uses this ability by using the castle to travel great distances in just a few seconds. He eventually uses the castle to kidnap the Hashira along with Tanjiro and friends when a door opens beneath everyone's feet, sucking them into the castle.

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How does Infinity Fortress work?

The Infinity Castle is actually a massive manifestation of Blood Demon Art! Whose you may ask? Well, this gigantic dimension is the Blood Demon Art of the Upper Moon, Nakime. She controls the castle with her biwa, a large stringed instrument that she plucks to make the corridors and walls move at will. While it is not explicitly confirmed whether the other demons inside know how to navigate the entire castle, it is clear that all the inhabitants inside are dependent on Nakime (except Muzan). However, there are instances, especially with the other upper moons, where demons familiar with the castle take full advantage of its gravity and strange structure to traverse different areas. No one knows how deep or wide the castle is as it is shown to constantly shift and move of its own accord. We got a glimpse of this depth in the scene where Akaza goes to the Upper Moon meeting and seemingly falls from hundreds of meters high, even passing through another castle in the middle of the water, before landing on what looks like a wall rising immediately from a pillar.

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What else can Infinity Fortress do?

Aside from looking like the shifting hallways of Hogwarts, the interior of the castle seems to exist in a separate dimension and is completely at the mercy of Nakime and her biwa. We're not sure if Muzan or Nakime need to know the location beforehand, but the castle can appear wherever they want as a door leading outside. It's clear that Nakime can move, hold, and lead people through the doors and hallways in the castle. We see this when Muzan is brought to the balcony outside the castle despite previously being deeper inside the building.

The castle also appears to be sentient to some extent. The walls and corridors are shown to constantly change at will, even when Nakime is not playing the biwa. The castle also serves as the main base of operations for the demons under Muzan's command, as the castle's innate structure blocks sunlight even at midday. Regardless of how large the castle actually is, one thing is certain: Being summoned to the Infinity Castle is a matter of survival.

Demon Slayer: Infinity Castle has now completed Season 4 on Netflix. You can watch the full season of Demon Slayer on Netflix.

David Pac

Update 11 December 2024