Arch-Enemy Event Weapon

The Nox Nyctores causality weapons (事象兵器アークエネミー, Jishō Heiki Āku Enemī, "Arch Enemy causality weapons") are a set of ten weapons.

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The final stage of Ars Armagus. These armagus were tempered as a set of close range and melee-type weapons to directly oppose the Black Beast. They are also known as "causality weapons". An advanced tempering technique was needed to forge them, and a total of ten weapons were planned.

The first nine were created during the First War of Magic, based on the Sankishin, to combat the Black Beast. Only those with the highest proficiency in the "Proper Use of Ars Magus" can wield them, and even then, there is a significant risk of mental burden on the user. It's said that the Nox choose their masters. One of the primary functions of Nox Nyctores is to unburden their owners of "needless" emotions and enhance others; this has a profound effect, for example eliminating fear, but owners may also find themselves losing their compassion, remorse, etc.

Among the Nox Nyctores, the Murakumo Unit is unique in that it was produced after the Dark War, and is actually an Anti-Sankishin Core Unit, created in a Cauldron as a means to make contact with the Boundary, where its soul exists. During the Ikaruga Federation's 12th attempt to produce one, together with a Sector Seven research team, the experiment was interrupted by an attack from the NOL's Nox: Gigant: Take-Mikazuchi and this resulted in the creation of Noel, in an incomplete state. Afterwards, three base bodies were stolen from the NOL and Nu was created in Kagutsuchi. Ragna's already destroyed the two others.

There are also imitation Nox Nyctores called artificial causality weapons. They rely on atomic power instead of the life energy used during the forging of the Nox. They are replicas, but have comparable power and are recognized by the Nox Nyctores as being similar. Jubei once experienced a resonance created by his Musashi when it came into contact with one. There is an upgraded version of the artificial causality weapon known as an "Idea Engine", but nothing else is known of it. There are a handful of other things that can stand up against Nox Nyctores.

No. 01
Owned by the NOL. Its form is that of an attack satellite. Take-Mikazuchi is a Japanese thunder god and patron saint of warriors. It is commonly mistaken to be The Black Beast itself. According to Continuum Shift, it was sealed away after the war due to fear of its use, contrary to it being fired at Kagutsuchi in Calamity Trigger. From Rachel's words, it seems as though Take-Mikazuchi can only fire once every four years.
 * Gigant: Take-Mikazuchi (Gigant: Raging-Crescent Moon)

No. 02
Owned by Jin Kisaragi. Its form is that of a Japanese sword. "Yukianesa", "snow woman", is a Japanese fairy. "Mucro" means the sharp tip of a sword, and "Algesco" means "to become cold". Continuum Shift states its blade is ice, and its power is manipulating the water in the atmosphere. According to Noel in Calamity Trigger, the ice Yukianesa creates erodes life, which explains why Jin seems to freeze everything for a short amount of time during his Astral Heat.
 * Mucro Algesco: Yukianesa (Ice Sword: Snow Woman)

No. 03
Owned by Noel Vermillion. Its form is that of a pair of handguns. Bolverk is Odin, disguised in his human form. According to Continuum Shift, it can attack targets through walls, Optic Barrel being a dimensional collapse of sorts at a point in line with the barrel. Bolverk also serves as a limiter for Noel that suppress her emotions which explains why she does not become emotionally unstable as Carl Clover or Jin Kisaragi. It is also revealed that in Noel's past she was attacked by a monster and suddenly Bolverk appeared right before her. In Continnum Shift's True Ending, Noel's emotions broke Bolverk unleashing Mu.
 * Arcus Diabolus: Bolverk (Majuu:Berubeku, Demon Pistols: Bolverk)

No. 04
Owned by Carl Clover. Its form is that of an automaton. Nirvana is a transcendent state of enlightenment and tranquility in Buddhism, and Deus Machina is a latin phrase meaning "god machine." Ada Clover's body was used in her creation.
 * Deus Machina: Nirvana (God Machine: Nirvana)

No. 05
Owned by Jubei. Its form is a pair of kodachis, one stored in each end of the sheath. It's apparently named after Musashi Miyamoto, a historical samurai known to fight using two swords in hand. Supposedly its power is to cut 'what cannot normally be cut', what this means is unclear. Though in Continuum Shift it's heavily impiled that it is able to destroy a magical field or barrier, or possibly anything it chooses to cut.
 * Mucro Somino: Musashi (Blades of Nothingness: Musashi)

No. 06
Owned by Hakumen. Its form is that of a nodachi. Ookami means "Howling God" or "wolf" depending on the reading. It can also mean "Great God" and is a frequent honorific used for Shinto gods. Interfectum Malus is a Latin phrase probably intended to mean "Evil Destroyed" or "Evil's Destruction". According to Continuum Shift, it is made of a metal that negates Ars Magus in a certain distance, explaining why Arakune can be killed by it in Calamity Trigger rather than reform. During the, Teach Me, Miss Litchi Reloaded episode, Ragna states that "it has yet to actually display its power".
 * Interfectum Malus: Ookami (Evil Slayer: Howling God)

No. 07
Owned by Platinum the Trinity. Muchourin means, very roughly, "Untolled Bell". Arma Reboare means, roughly, "Ringing Weapon" or "Resounding Weapon" in Latin. Its abilities are the incarnation of matter. In the Teach me Miss Litchi segement in Continuum Shift, Luna mentions using it will cause her to lose memories. Whether this means temporary loss or complete amnesia is uncertain.
 * Arma Reboare: Muchourin (Resounding Weapon: Untolled Bell)

No. 08
Owned by Terumi Yuuki. Its form is that of a black snake head attached to a never-ending chain. Ouroboros is the symbol of a snake eating or biting its own tail, symbolizing infinity. It is believed that this Nox Nyctores can directly attack the mind and psyche of the victim. Geminus Anguium is a Latin phrase meaning "Twin Snakes", though 'twin' is, oddly, singular.
 * Geminus Anguium: Ouroboros (Snake Claw: Ouroboros)

No. 09
Owned by Bang Shishigami. It is believed to possess the power to destroy other Nox weapons as well as sever ties with the Boundary, but only Platinum knows what happened to it since the war (Bang is unaware of its power, though they can possibly be his gauntlets, giant nail or his belt buckle).
 * Phoenix: Rettenjō (Hoyoku: Rettenjō, Phoenix Wing: Violent Heaven's Maiden)

No. 10
Owned by Nu-13, and later, Mu-12. Its form is that of a huge sword that can transform into armor; it is actually the Murakumo Unit's "true form". Lambda-11 is an imitation Murakumo Unit and uses the Idea Engine instead. Murakumo means "Gathering Clouds", derived from Ama no Murakumo no Tsurugi (Kusanagi no Tsurugi), the "Sword of the Gathering Clouds of Heaven". Lux Sanctus is a Latin phrase roughly translating to "holy light".
 * Lux Sanctus: Murakumo (Divine Power: Gathering Clouds)