Crimson Moon

Brunestud of the Crimson Moon (朱い月のブリュンスタッド). also called Crimson Moon (朱い月), is the Ultimate One of the Moon (月のアルテミット・ワン), classified as the Type-Moon (タイプ・ムーン) Aristoteles. He responded to a call from the collective will of the earth, Gaia, over four thousand years ago, and made a deal to allow for him to live on the Earth in exchange for protection against human corruption. The planet, unable to use a mirror to reflect itself, is unable to set its own standards, so only another celestial body is able to understand the death of a celestial body. True Ancestors based in his image were created as a natural protective system for the earth, and were set to return it to its natural state. Brunestud traveled the planet, challenged random beings to defeat him, such as Gransurg Blackmore, who was nothing but an average magus, and the villagers holding Merem Solomon. He also gathered a number of followers, such as Blackmore and Trhvmn Ortenrosse, in an attempt to eventually take the earth as his own kingdom. He was eventually defeated by Kischur Zelretch Schweinorg wielding Second Magic. He is the one behind the state of the world of Notes, and would appear before the "final boss."

He holds a Reality Marble, part of which contains the Millennium Castle Brunestud, the Noble Color of Rainbow, the ability to use a skill called Alt Nagel (アルトネーゲル), which is described as an immensely destructive pillar of wind which stretches as far as the heavens, and a Knight Arm called Real of the World (リアル・オブ・ザ・ワールド（真世界）), which is also the title of the True Ancestors' purpose of restoring the world to its natural state. All creatures known as Dead Apostles are descended from him in some way, and as with True Ancestors, he can create strong Dead Apostles by drinking the blood of a human, having created at least two members of The Twenty-seven Dead Apostle Ancestors, Merem and Zelretch, and having had both Blackmore and Ortenrosse become vampires through magical research in order to follow him. Despite the impact the Twenty-seven Ancestors have on the planet, they can be considered nothing more than a footprint that he made on the world. He holds some sort of control over the moon itself, allowing him to cause the Moon Fall (月落とし), where the moon fell towards the planet. It was pushed back by Zelretch's magic, so it was unable to affect the planet. With all of his power, Brunestud did not foresee being defeated by a human, but lost to Zelretch due to being too late in understanding the power of Magic, "a rule outside of the rules."

Brunestud foresaw that his own life was reaching its end due to having too many enemies, as he has a "world corrosive will" that does not abide by either Gaia or Alaya. He desperately wished to have a vessel that abides by the standards of the world, and planned to use the True Ancestors in preparation for his extermination. They are considered to be spirits of nature accepted by Gaia, and even though they are considered the enemies of humanity, the subconsciousness of humans both accepts and denies them as keepers of nature, causing them not to be marked as targets of elimination for the Beasts of Alaya. Normally they were only created by the planet out of necessity, but Brunestud decided to teach them how to make their own kind themselves in order to speed up the creation of a proper vessel. He sought various other possibilities when an heir in the form a True Ancestor could not be born, such as the creation of Altrouge Brunestud, a being born between a Dead Apostle and a True Ancestor. While he was destroyed by Zelretch before the creation of a perfect vessel could be realized, he still has a method for revival. His Reality Marble has been left behind to spawn the True Ancestors, allowing them to inherit a "seed" on which he can imbed himself. Its purpose is so that when a True Ancestor reaches the same purity as him and body of his scale, the Reality Marble allow him to take over their bodies through spiritual possession. Michael Roa Valdamjong considers this to be an inefficient method compared to his own means of resurrection, as it is hard for a being on such a scale to be brought into existence.

Altrouge and Arcueid Brunestud, who have both inherited the Brunestud name, are considered to be those closest to reaching the point of being suitable vessels. Arcueid, created naturally by the True Ancestors, a method which Brunestud had given up on at the time, is considered a perfect body especially close in purity as she can summon the Millennium Castle through her Marble Phantasm ability. Altrouge still lacks the right amount of power and she is considered too unstable, though her control over Primate Murder can give her the right to be called a greater monster more powerful than Brunestud himself in a way. While the True Ancestors were his "children" based off of him, only he can be considered perfect, while all of them are considered failures. This is the cause of their blood-lust, their corruption upon feasting on humans, and their connection to the moon. Each has a piece of Crimson Moon inside them and a place to accept him, which manifests in Arcueid as a type of alternate personality hiding inside of her consciousness waiting to fuse with its host. It takes the form of Arcueid's initial state before having her hair removed, and it is able to move around the Millennium Castle while she sleeps. It also stays active in her unconsciousness, such as when Tohno Shiki connects to her dreams in Kagetsu Tohya.

It is unable to fuse with her while she sleeps in the castle, as she is not currently in a state to accept him, and admits to Roa that, while identifying itself as Crimson Moon, it is still nothing more than an aspect of it. Every True Ancestor is an incarnation of Crimson Moon, but at the same time, they are totally different beings. The part inside Arcueid is nothing more than a shadow of her that only exists as a hologram that has possibility. It is not yet confirmed as "Crimson Moon", as it cannot become "Crimson Moon" while "Arcueid Brunestud" is still identified as "Arcueid Brunestud." It realizes it itself didn't know exactly where it stood, and states "And to think I was planning to take over." While it wishes for Roa to unbind Arcueid's chains, he speculates that as long as Arcueid is bound in her own chains, that she will eventually give up her name. This personality speaks to Shiki briefly, amazed that humans are such noisy creatures, and that Arcueid can get along with such an "impolite person." It tries to insist that it is separate from Arcueid, that it is only an aspect of her that is separate from her at the same time. Shiki identifies that while it has long hair and speaks with an accent, and even as just an aspect of her, that it still is Arcueid. It is amazed by those words, as someone who would see Crimson Moon as an enemy who will take Arcueid's body is still using words that affirm its existence. Accepting the enemy means that Crimson Moon is near, to which Shiki replies that he will simply take her back by force. While "fighting with Arcueid to save Arcueid" can be considered a contradiction, he states that he will fight it, and save the Arcueid who has been bound by her own chains. It responds to him with "I hope your words will come to be more than just a simple joke" in a tone that seems like an awkward request betraying her noble self.