Black Imperial Sword Judecca

The  is a sentient Demon Lord Weapon originally sealed in the Sky Library before contracting with Arata Kasuga. Since then, Judecca has supported her master and eventualy became one of his primary weapons used in battles.

Personality
Upon being released from her seal, Judecca initially behaved similarly to an automated artifical intelligence system. However, after forming a contract with Arata, her responses gradually became more diverse and less robotic. As a Demon Lord Weapon, she will faithfully follow her master's desires and strive to fufill his wishes. In particular, she will even indulge with Arata's perversion.

During battles, Judecca can provide guidance and analyze the situation to offer the best course of action.

After taking on her human form, she acts very affectionate and tries to flirt with him. However, she usually ignores all other people except her master.

Sword
Judecca's true form is a longsword consisting of a jagged blade with a hook at the tip. Inside the crossguard contains a round gem that stores Judecca's conscience which allows her to communicate with other people. Attached to the pommel of grip is a long skeletal lanyard that can enfold the user's arm for analysis.

After Arata changes his class to that of a Sword Magus, he gained the capability to load spells from the Trinity Seven into Judecca, thus alternating her form as well.
 * Fides of Gula - Large medieval blade with a cover guard and long grip.

Human
In her human form she takes an appearance of a young girl in her teens with long white hair and purple eyes. As with most girls in the series she has large breasts. Judecca wears short white one-piece dress. Her other unusual feature is her short pointy ears.

History
A long time ago, Judecca was sealed by the Spriggans who would guard the Demon Lord Weapon inside the Sky Library for many years. Even after Abyss Trinity destroyed Akio's hometown, Judecca would continue to slumber within the Library.

Sky Library
Inside the sealed Judecca's room, Abyss Trinity observes Arata's party before recognizing his daughter, Lilith.

Some time later, while struggling against the golem, Arata and Akio are unexpectedly forced back into Judecca's room. They initialy are unaware of the Demon Lord Weapon's presence until Lieselotte warns them after sensing the sword's existence. While Lugh and the rest of the group stall the golem, Arata approaches Judecca whose seal suddenly breaks and falls into his hand. Upon contact, Judecca quickly confirms Arata possesses a Demon Lord Element before analyzing his magic. However, after detecting only his Archive Superbia along with Luxuria and Gula, she states that Arata has not yet achieved the Trinity requirement. As a result, Judecca then begins the process to force the Demon Lord within Arata to awaken. Akio attempts to separate the two, however Judecca easily repels her, forcing the ex-Spriggan to use the camera containing Lieselotte to freeze time.

Within the Frozen World, after noticing his arm has partially transformed into the Demon Lord, Lieselotte comments that even if time has frozen, the transformation slowly continues to progress. Arata then forcibly releases Judecca and returns to normal, much to grimoire's concern.

Later, after Arata successfully masters Lieselotte's Logos Art and returns with her to the real world, he then summons Judecca who confirms that he has mastered the Trinity before deeming him as her master. Next, he questions if she can defeat the golem which she verifies that she can easily destroy the target. Arata begins concentrating while wielding Judecca, causing his magic to disappear for a moment before quietly eliminating the golem. Arata comments that he is finally understanding how to use magic as a result of using Judecca. Afterwards, Lugh tries to touch Judecca, the sword binds the thief and erotically absorbs her magic.

While Abyss Trinity attempts to awaken Lilith's Last Key, Arata surprised the Demon Lord and uses Judecca to force him back. However, Abyss easily recovers from the attack while brandishing the Red Imperial Sword Caina. Arata, with Judecca, and Abyss, with Caina, then begin clashing with one another, causing destruction to their surroundings. As Abyss orders Caina to invoke his "Fall" magic, Arata nevertheless continues to confront the Crimson Demon Lord while his grimoires analyze, despite receiving minor damange. After Sora and Ilia reveal the nature of the "Fall" Thema, Arata commands Judecca to execute Akio's magic, imbuing herself with Mantra Enchant. Disabling Abyss' magic with his anti-magic, Arata manages to force the Demon Lord back with the strengthened Judecca, destroying nearly half of Sky Library. However, after Abyss forcibly awakens the Demon Lord Element within Lilith in order to regain his original strength, Arata and Judecca find themselves eventually ensnared by his magic. Arata and the grimoires decide to use anti-magic to escape, but Judecca states that his chances are quite small, much to his chagrin. Regardless, along with Akio and Lieselott'e support, Arata manages to liberate Lilith from Abyss' control, as well as gain his fourth Archive and transform into the Trinity Form. In his final strike, Arata uses Judecca to destroy both Abyss Trinity and the Sky Library.

After Finding himself in Akio's ruined hometown again, he questions the whereabouts of Judeccca who reveals herself as a small pendant, confirming the destruction of Sky Library as well as the ability to change into any form of his choosing. When he asks the type of girl she can transform into, the Demon Lord Weapon responds "a very bouncy one", much to Arata's happiness and Lilith's displeasure.

Abilities
As a Demon Lord Weapon, Judecca can only be wielded by a Demon Lord or Demon Lord Candidate who has achieved the Trinity and possesses the Thema Imperium. Thus, the only individual who wield her is Arata Kasuga. However,if the requirements are not satisfied, she will initate Berserk Mode, which attempts to forcibly awaken the Demon Lord within the user. If someone tries to interfere the process, Judecca then can repel the transgressors, causing them slight damage. The only way to completely halt Berserk Mode is for the possessor to release Judecca which will restore the person to normal. Otherwise, the transformation will continue to progress, even if time itself is frozen.

However, upon successfully forming a contract, Judecca will become loyal to her master, providing guidance and support to fufill her owner's desire. Judecca can quickly analyze an opponent or the situation, as well as advice on a course of action. Furthermore, her ability enables the user to perform Paladin level techniques, such as supressing their magic before unleashing it all at once so quickly before anyone realizes. The release is quite large that even inviduals far away can sense the magic. Judecca enables her master to cast several different types of magic at the same time. While wielding Judecca, the possessor is also able to swiftly overview the surrounding area. Furthermore, as the embodiment of the Fourth Gate, Judecca can allow her master to surpass the Trinity.

Judecca, according to her master's commands, can perform imbue herself with magic from any of her master's Archive, such as combining with Mantra Enchant will increase Judecca's strength.

As a Demon Lord Weapon, Judecca can channel a great amount of magic, unleashing devastation sufficient enough to destroy even the Sky Library. If the master wields Judecca effectively, she can overcome and force back against even a Demon Lord.

If someone other than her master attempts to touch her, Judecca will bind the perpetrator and begin leeching the person's magic.

Additionally, Judecca can transform into any form of her master's choosing, including a a pendant version of herself. She has also hinted at being able to assume a human female form if necessary.

After her master relinquished his Demon Lord Element, Judecca could no longer be utilized, temporarily falling under Abyss Trinity's care for awhile. However, Arata later regained the right to wield her after partially merging with the Weapon, allowing access to her abundant resource of magic. Furthermore, upon becoming a Sword Magus, Arata is capable of loading his spells into Judecca to invoke from, causing her form to morph as well.

However, because his magic has capable of overwhelming even grimoires, Judecca maintains control over her master's strength which can become erratic when Arata becomes irritated.

Techniques

 * L'Ciel Cocytus - While charging herself, the possessor performs a powerful stike capable of destroying the Sky Library. Alternatively, the wielder can also summon large amount of anti-magic in an area to dispell a Paladin's magic or even a Final Crest.
 * Imperiosus Magister - Tansfers her master's magic into another individual at the result of losing the Demon Lord Element, rendering the possessor a normal human or even disppearing in a worst case scenario.
 * L'Ciel Ascella Cocytus - Together with Caina, Judecca's master executes two powerful simulataneous slashes capable of destroying two Breakdown Phenomenons.

Gula

 * Conception - Generates a powerful energy wave to strike an opponent from a distance.

Relationships
Arata Kasuga -  As her master, Arata wields Judecca during battle while she provides support and guidance. The two first enountered one another when Arata accidentally was forced into the room she was sealed within. Upon approaching the Demon Lord Weapon, Judecca's seal would break and fall itno Arata's possession. However, determining that Arata did not meet the Trinity requirements, she then attempted to force the Demon Lord within him to awaken until Lieselotte intervened. Nevertheless, Arata would later successfully form a contract with Judecca after copying Lieselotte's magic.

Despite forming a contract for relatively short amount of time, Arata has shown to wield Judecca quite effectively, capable of holding his own against the Demon Lord Abyss Trinity. Normally during battles, Arata will usually give instructions to Judecca which she will loyally process. Furthermore, Judecca will also provide information about the enemies and situation, as well as suggest the best possible course of actions to follow. Additionally, the two are on friendly terms, with Judecca even indulging in Arata's perversion.

Notably, Arata is the only person capable of wielding Judecca since the master must match her Thema Imperium.

Trivia

 * Due to her status as a Demon Lord Weapon which dictates that only one Demon Lord can wield her in all time and worlds, there is only one version of Judecca that exists even across alternative dimensions and parallel universes.