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.

In BlazBlue: Continuum Shift - Extend's Extra Story, "That Which Is Inherited", it is revealed that The catalyst to smelt a Nox Nyctores are human souls. Sometime before the destruction 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 were discussing the creation of an Artificial Identity from above the Sector Seven's cauldron, it was shown that by smelting an Artificial Identity (AI) 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 dertermines 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 seither (Fluid Seithr 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, NOL forces attack Sector Seven's base in order to interrupt the smelting process and retrieve Nirvana. Relius carries on with the experiment and opens the cauldron, revealing a black object. With its destructive power, the Black 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, Nine had originally created a Black Beast to defeat another Black Beast during the War. As the black object 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 Nine's spell Snap Weapon: 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 Relius, 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 phenomenon weapons. They rely on atomic power instead of the life energy (human souls) 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.