Arch-Enemy Event Weapon

The Nox Nyctores Causality Weapons (事象兵器アークエネミー), also known simply as Nox Nyctores and the Causality Weapons (事象兵器), are a set of eleven weapons, and 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. An advanced tempering technique was needed to forge them, and a total of ten weapons were planned.

Information
The first nine were created during the First War of Ars Magus, 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 is said that the Nox Nyctores choose their masters.

Just like Magic attacks, they also cause scarring of the Soul.

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. Strong-willed individuals such as Hakumen and Jūbei seem to be highly unaffected by this side-effect, however.

While being powerful enough to fight the Black Beast, Nox Nyctores are affected by the Boundary. If a Nox with a released core is put near the Cauldron, its ability will not activate at all.

Among the Nox Nyctores, the Murakumo Unit is unique in that it was produced after the First War of Ars Magus, 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 Novus Orbis Librarium's Nox Nyctores, Gigant: Takemikazuchi, and this resulted in the creation of Noel Vermillion, in an incomplete state. Afterwards, three base bodies were stolen from the NOL and Nu -No. 13- was created in 13th Hierarchical City of Kagutsuchi. Ragna the Bloodedge already destroyed the two others.

The catalyst to smelt a Nox Nyctores are human souls. Sometime before the destruction of 5th Hierarchical City of Ibukido, Sector Seven's professor Kokonoe was paid a visit by Relius Clover, who wanted to build a Nox Nyctores.

As Kokonoe and Relius Clover were discussing the creation of an Artificial Identity from above the Sector Seven's cauldron, it was shown that by smelting an Artificial Identity deep within the Boundary, it is able to observe itself and refine its existence. The stronger the observation, the stronger its value as a weapon it becomes. Depending on whether it takes the observation multiple or individual ways, is what determines its viability as a weapon. Observing its soul in multiple ways would make it more effective as a weapon, enabling it to make multiple observations simultaneously. The core's smelting process involves compressing the seithr ('Seithr Fluid Body Theory') into its threshold limit, forming a unit, and is then implanted with a "soul". In concept, this process is similar to smelting the core of a causality weapon.

As the final smelting in the Cauldron is about to end, the Novus Orbis Librarium forces attack Sector Seven's base in order to interrupt the smelting process and retrieve Deus Machina: Nirvana. Relius carries on with the experiment and opens the cauldron, revealing a Black Beast. With its destructive power, the Beast begins snatching up and consuming NOL soldiers and is about to begin a massive killing spree. Relius remarks that the core of a Nox Nyctores is the Black Beast itself and that Kokonoe's mother, Konoe A. Mercury, had originally created a Black Beast to defeat another Black Beast during the Dark War. As the Beast is about to attack Kokonoe and Relius, Nirvana and Ignis (through the use of a powertrain) are able to knockback the Beast. Relius then urges Kokonoe to seal the Black Beast using her mother's spell Infinite Gravity. Magic orbs begin to surround the cauldron, causing one of the coffins containg the Prime Field Device, subject 13. (who had just been created before the following events) to burst. The Black Beast is compressed into the size of an apple. Relius ponders on whether he can recreate the Black Beast if he used subjects 11 and 12. Relius orders Ignis to retrieve the compressed black sphere (soul). As Ignis reaches out for it, Kokonoe takes control of Nirvana with magic. As Ignis is unable to defend Relius, Nirvana lunges one of her arms at him, piercing the right side of his abdomen. Astonished by this, Relius wonders if this was caused by some form of intervention.

There are also imitation Nox Nyctores called Artificial Causality Weapons. They rely on atomic power instead of the life energy (human souls) used during the forging of the Nox Nyctores. They are replicas, but have comparable power and are recognized by the Nox Nyctores as being similar. Jūbei once experienced a resonance created by his Mucro Somnio: 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.

List of all known Nox Nyctores

 * 1) Gigant: Takemikazuchi (・タケミカヅチ) — A giant humanoid, who later was sealed within a satellite and sent away from the world. Eventually it was turned into the Embryo. Its core was used for the Nox Nyctores number 2-9. It was wielded by the Takamagahara System, and also temporarily by Hades: Izanami.
 * 2) Mucro Algesco: Yukianesa (氷剣・ユキアネサ) — A katana with the blade made of ice. It is wielded by Jin Kisaragi, and previously by Seven.
 * 3) Arcus Diabolus: Bolverk (魔銃・ベルヴェルク) — A pair of handguns with the power to pierce through space. It is wielded by Noel Vermillion, and previously by Three.
 * 4) Deus Machina: Nirvana (機神・ニルヴァーナ) — An automaton with a female appearance. Nirvana has her nails made of a material that negates Ars Magus. It is wielded by Carl Clover, and previously by Celica A. Mercury.
 * 5) Mucro Somnio: Musashi (夢刀・六三四) — A pair of kodachis. Musashi's power is to cut "what cannot normally be cut". It is wielded by Jūbei.
 * 6) Interfectum Malus: Ōkami (斬魔・鳴神) — A nodachi with the blade made of a metal that negates Ars Magus. It is wielded by Izayoi, and previously by Hakumen.
 * 7) Arma Reboare: Muchōrin (雷轟・無兆鈴) — A wand that appears to be as long as its wielder. Its abilities are the incarnation of matter. It was wielded by Trinity Glassfille, and then Platinum the Trinity. It is unknown what happened to Muchōrin after materializing the latest thing, Hihiirokane weapon.
 * 8) Geminus Anguium: Ouroboros (蛇双・ウロボロス) — A never-ending chain with a snake's head. It can cause direct damage to the victim's mind. It is wielded by Hazama Honoka, and previously also by Yūki Terumi and Kazuma Kval.
 * 9) Phoenix: Rettenjō (鳳翼・烈天上) — A giant 55-inch nail. It is an Anti-Nox Nyctores weapon, and the core of Kushinada's Lynchpin, which has the ability to stop the functionality of seithr. It is wielded by Bang Shishigami.
 * 10) Lux Sanctus: Murakumo (神輝・ムラクモ) — A large sword which transforms into the armor and eight floating blades. This weapon was created after the Dark War, so it is the only Nox Nyctores without a part of Takemikazuchi's core. This type of weapon is wielded by the Murakumo Unit.
 * 11) Corpus Sepulcro: Requiem (骸葬・レクイエム) — A giant humanoid. It was made to replace the Amaterasu Unit, and create the new world that is not based on Amaterasu's dreams. Requiem was supposed to serve as a new god, a perfect system which doesn't have emotions, so the world would not have the Phenomenon Interventions. This weapon wasn't completed, and eventually was destroyed.

Trivia

 * This set of weapons is called in the Japanese version as Arch-Enemy Event Weapons. An "arch-enemy" is the principal enemy of someone or something.
 * This set of weapons is called in the English version as Nox Nyctores Causality Weapons. "Nox Nyctores" is a term made of three words: "nox" – Latin word for night, "nycto" – Greek word for night, "res" – Latin word for thing.