Azure Wind Blade

The «Azure Wind Blade» (の剣) is a «Priority» 47-class «Divine Object» longsword, a gift given by Shinku of the Asanagi Shrine to the Rosenberg Crown in the year 774. It is the personal weapon of Emilia Rosenberg, the first user of the Divine Object in three hundred years.

Background
It is written in the historical texts that Typhoon Kajiki, an extremely powerful storm struck the Kiyotō Empire, wreaking havoc across the nation over a duration of three days from the Thirteenth to the Sixteenth Days of the Ninth Month, in the year 773. Shinku, then aged 150, was ordered by Emperor Kansho Suisei to utilize her Sacred Arts rituals to transform the storm into an item, as he wanted to harness the power of nature for the empire.

Although she obeyed, Shinku had no intention of giving the completed sword to the emperor due to his power-hungry nature. As a result, Shinku faked destroying the sword after she had created it in a presentation to the emperor. After escaping, she fled to the Flavan Kingdom where she gave the newly christened «Azure Wind Blade» as a present to Zacharias Rosenberg on the Fourteenth Day of the First Month, 774, the first and only user of the Divine Object until three hundred years later when one of his descendants, Emilia Rosenberg, was able to lift and use the sword with exceptional talent.

Through her own speculations, Emilia surmised that her ability to wield the weapon must be because she was acknowledged as a worthy wielder whereas past wielder hopefuls did have high enough «Object Control Authorities» to wield the weapon but they either did not have the skill to use it properly or the Divine Object itself denied them as worthy wielders.

Abilities
As a «Priority» 47-class weapon, the Azure Wind Blade has exceptional strength and cutting power, seen when it was able to easily fell the Oak of Antinia, said to be unable to be cut down due to its uncanny ability to absorb the spatial resources from both the ground and the sky, raising its durability to absurd levels. It also has incredible piercing power shown when it stabbed straight through the skin of an elder dragon although this feat was accomplished using an Incarnation-enhanced «Vorpal Strike». The Azure Wind Blade also has no single elemental weakness, shown in multiple occasions where it was able to cut through every single element, even Fire (although sword skills are probably to blame). Its high priority class also allowed it to use Sword Skills of up to five consecutive hits, when wielded by a competent swordsman, although when in the hands of Emilia, seven-hit combos are possible.

Armament Full Control Art
Due to having two users that have individually performed this high-level Sacred Art, the Azure Wind Blade has two different manifestations of its Armament Full Control Art.

Zacharias's Version
When the Armament Full Control Art is in effect, the sword essentially turns into a localized tornado, capable of heavily increasing Zacharias's speed. In the «enhancing» stage, the sword becomes a tangible maelstrom. Although it is completely composed out of strong winds, it is still very much capable of crossing with material swords, although, the question of whether or not the material sword remains intact after colliding with the enhanced Azure Wind Blade is another matter entirely. Using this, Zacharias can encase himself in a cocoon of wind which allows him to move at unimaginable speeds, using a sudden burst of air from the sword to propel him forwards.

Zacharias has only used the second «releasing» stage only once in his lifetime in the Battle of Amberdenn Bay. In this decisive naval battle, Zacharias had the Azure Wind Blade absorb all the air, causing a drastic depressurization of the atmosphere in the area which pulled all of the enemy's ships in his direction before releasing a single powerful airblast that created a crater in the water, 150 meters wide and 60 meters deep.

Emilia's Version
When the Armament Full Control Art is in effect, the sword turns into a translucent blade of air. Under Emilia's direction, this «enhancing» stage allows her to create multiple blades composed of wind that she can then direct using her mind. She does this by tracing a semicircle over her head from left to right which creates the blades of wind like the slats of a handheld fan. She could attach the blades to her back to create wings, allowing her to take flight.

In the second «releasing» stage, Emilia's sword turns directly into a hurricane. Due to it being a powerful force of nature, the slightest slip in her concentration would be enough to loose the phenomenon from her control which would then proceed to wreak unprecedented havoc. However, while under her control, Emilia could direct the destruction in one direction.

Appearance
The Azure Wind Blade is a sky blue double-edged longsword, exactly 118 centimeters in length.

Alicization Inviting
As per the custom of the House of Rosenberg, the twelve-year-old Emilia was educated in the romantic history of the Azure Wind Blade in preparation for the traditional ceremony where a Rosenberg child would attempt to extract the sword from its resting place, thrust into an especially durable adamantite deposit by Zacharias Rosenberg. For the first time in three hundred years, the Azure Wind Blade is withdrawn from its resting place.

As the inheritor of the Azure Wind Blade, Emilia displayed her exceptional skill at wielding the blade at a public event, showing off unprecedented combos with Secret Maneuvers, numbering in the four-, five-, and six-hit combos via «Divine Quadrangular Prism», «Violet Asterisk», and «Demon Lord Pentagram», respectively. As the Crown Princess, her popularity increased further with this revelation.

Trivia

 * The blade and hilt of the sword are able to grow several centimeters, turning the originally one-handed sword into a two-handed one.