Corpse Shell

Corpse Shell (鬼の力 (コープス・シェル), Kōpusu Sheru lit. Devil's Power), also known as the Devil Factor (鬼の因子, Oni no Inshi), was a special Black Art that was classified as a "Forbidden Magic", akin to that of Abyss Break and Nirvana. It was known as a Bloodline Magic, due to being completely unique to the Sejren Family; however, the origins of Corpse Shell were something far darker than initially imagined. However, while it is not 'inherited', it does exist in the form of a Corpse Curse Brand (骸呪烙印, Gaijū Rakuin); a special magical glyph containing negatively-charged magical energy that is applied to the inheritor's body, granting them the power of Corpse Shell. Corpse Shell allowed for a person to have a parasite/host type relationship with the demon known as Abyssion, and Corpse Shell will allow the user to transform into a demonic figure with incredible powers and back; at the cost of the users' sanity.

History
After continued losses to the likes of dragons in the Human-Dragon War and the deaths of many of her comrades, Jeanne Sejren, the very first history-important member of the Sejren Family, in her desperation as her Factor of the Dragon was not enough to kill a dragon, summoned an Etherious demon known as Abyssion, who was forged from one of the Books of Amadam—Abyssion, tier-wise, was at least as powerful as the Ancient Ones known as Origin and Varian. Making a contract with the demon, Jeanne was given a sample of Abyssion's blood which was infused within her bloodstream, which was actually a concentrated version of negatively-charged magical energy; demon blood. Since the Factor of the Dragon allowed her human body to resist demonic corruption to a certain extent, Jeanne was capable of mixing the negatively-charged magical energy with her draconic magical energy in order to forge a new Black Art; Corpse Shell.

After Jeanne's death, her body was split into six parts and the Sejren Family head of the time managed to obtain a portion of Jeanne's negatively-charged magical energy-tainted draconic blood. Taking the blood, the Sejren Family head used their Sealing Magic in order to create a seal powerful enough to contain the negatively-charged magical energy, sealing said particles within the formation of the seal; calling it the Corpse Curse Brand (骸呪烙印, Gaijū Rakuin). This Corpse Curse Brand was implanted upon the newest head in the Sejren Clan upon birth, granting them a symbiotic link with Abyssion from the moment they are born into this world. However, Abyssion can possess the person at any given time during the person's lifespan, even while still in their mother's womb or (apparently) just after death.

Description and Weaknesses
Corpse Shell was an unfathomably evil power, coming from the recesses of a heart stained with darkness; a darkness so thick that none could hope to escape from it's tainting influence. Essentially, in order to harness the power of Corpse Shell, the user would have to allow the lingering fragments of the negatively-charged magical energy located within their magic origin to emerge, taking over any traces of magical energy that the user could exude, with their draconic blood holding back the negatively-charged magical energy's corrupting influence, while also enabling the user to project it outwards, around their body. This took the form of a pitch-black aura of darkness which surrounded and compressed around their body, distorting their figure into a demonic shell of its humanized self. Normally, Corpse Shell took the form of the user gaining black slashes which form under their eyes, which then thicken noticeably and merge with the shadows formed on their face, which became stylized black; their skin tone also became much darker. The user's entire body turned a horrific pitch-black, with crimson markings around their chest, arms, as well as under and above their eyes. Finally, their hair would spike on end and grew out as twin chains manifested upon their arms. However, some members of the Sejren Family had vastly differing Corpse Shell forms; most notable was Jeanne's own form, which she used to end the Human-Dragon War.

However, for all the physical might and versatility that Corpse Shell provides, it did have one, horribly glaring, weakness—the origins of the magic itself. As Corpse Shell was created through a contract with an Etherious demon who provided negatively-charged magical energy in order to forge the magic, whenever a magician used Corpse Shell, they were tapping into the negatively-charged magical energy, which were toxic to regular magicians. Thanks to their "conditioning", the magicians of the Sejren Family who harnessed the Black Art were slightly resistant to the energies of demons, but since they were harnessing it with the bodies of humans, instead of destroying them from the inside-out horribly, it had a far more sinister effect—slowly, but surely, the negatively-charged magical energy would replace their regular magical energy, corroding their magic origin as their body's physiology slowly changed into that of a demon. This would cause them to forget their own sense of identity, as they became a rampaging monster—just as Abyssion intended.

There were a scarse few ways to avoid this fate; such as using a medium to carry the burden. An example of this would have been the relationship between Excellen Kilekion and Tsuruko Sejren in the original plans for Daybreak. When first activating Corpse Shell, as it took place in the exact same arc where Tsuruko became Gaiki for first time, since Excellen was there, and Tsuruko already had the Hellion known as Star Phoenix sealed within her, Abyssion would have immediately linked to Excellen instead, as her exalted and esper blood could have withstood the degenerative effects of Corpse Shell, causing her to unwittingly become the medium, and thus whenever Tsuruko harnessed Corpse Shell, Excellen would have suffered its effects instead of Tsuruko. The medium method has not shown up in the Sun Trilogy properly, however. To fully remove the corrupting influence of Abyssion, the users of Corpse Shell would have to forge a contract with a true demon; who would bless them with an annulled corruption, allowing them to use the magic to their heart's desire. Aside from those methods, there was no way to reverse or stop Demonization, leaving the users of Corpse Shell with the only option to not use the Black Art in the first place.

Powers and Abilities
Berserk (暴走 (ベルセルク), Beruseruku lit. Out of Control): Berserk was a status ailment that Corpse Shell grants an untrained user, whether or not they want to accept it. Upon activation of Corpse Shell, the corrupting influence of Abyssion would begin to seep into the user's brain, causing them to display a savage, nearly animalistic battle frenzy in which the user's strength and capabilities would dramatically increase. This special effect of Corpse Shell made it seem as if the magic was a vastly more superior version of Mask of Truth—though in reality, the two magics couldn't be further apart. However, it should be taken into consideration that once trained, a user of Corpse Shell was able to activate Berserk on a whim, and unlike the untrained version, an experienced magician did not feel fatigued by its usage; they also showed relative amounts of restraint, as some users were capable of controlling who and what they see as a target. Berserk increased the user's physical parameters to the point that every step that they took would cause a rippling shockwave to be released from their feet, and they were capable of smashing through almost any defenses, either physical or magical, with their bare hands. Indeed, during the Esper Excellen Part II arc, when the Dracolich attacked Luin, Marisa Sejren in Corpse Shell form was shown to be able to effortlessly tear draconic beings in half with her bare hands. In addition, Berserk allowed the user to ignore all senses of pain, even shrugging off the loss of a limb. In that way, it could be considered akin to 'super armour' of fighting games.

Enhanced Physical Prowess: When in Corpse Shell; the users' attributes were drastically enhanced; because, with a simple swing of their weapon, the user was capable of manifesting a violent tremor that obliterated the ground it came into contact with and knocked their foes away; in addition, their blows with their weapon and unarmed were positively overwhelming and could be bone-shattering. The sudden boost in strength upon activating the form allowed the user to break free from any attack which bound them or prevented them from moving. The user could grab a blade with their bare hand without feeling any of the exerted force, though said force could do considerable damage to the surrounding area. In addition, their endurance had been upped significantly; enabling the user to receive damage like it was nothing and ignore all senses of pain—though it should be noted that this varied on the factor of how powerful the blow was. Finally, the Sejren Family member's naturally immense swiftness was augmented to the point that they discarded any need for speed-enhancing techniques, enabling them to outstrip almost anyone in a contest of pure speed. What is interesting to note is that the negatively-charged magical energy enhanced all of the user's moves, greatly increasing their area-of-effect as well as improving their damage.

Enhanced Magical Prowess: Naturally, Corpse Shell also bolstered the user's magical power to the point that it could be considered leaps and bounds above any other magician's. This drastically increased the area-of-effect of any spell that the user casted, and the overall power of the spell; this is best shown with Crux Kouga's Arrow of Light spell, which, normally, would pierce the opponent and then vanish, but in Corpse Shell form, the Arrow of Light is able to drill through nearly any defense and pierce several opponents in a row before it vanishes. Another plus to having their magical energy augmented was that they gained the ability to perform "advanced" versions of their regular spells or new spells entirely; another example regarding Crux is his Ain Soph Aur spell, which is essentially an amalgamation of all of his previous Light Magic spells. However, due to the demonic influence of Abyssion, all of the user's attacks gained a certain black/red tint to it as the spells pulsed ominously, showing the demon's power. When in this form, the user was able to manipulate nonliving matter by changing its atom structure through the sheer force of their aura, i.e. turning air into a wall of water or turning a stone column into a large uprising spike.

Darkness Magic (闇の魔法, Yami no Mahō): In Corpse Shell form, the user gained access to a supreme form of Darkness Magic; granting them complete dominance over the element of darkness—when this energy interacted with the atmosphere it energized and accelerated the ambient magical particles, transforming them into a thick aura of scarlet darkness, befitting the user's demonic power. This new energy had an absolutely overwhelming amount of destructive power; it was capable of dishing out damage on the molecular level, disintegrating anything that it touched with relative ease; but to those who survived this darkness, there was something much worse. Unlike the superficial darkness of any other darkness-based skills, this scarlet darkness acted as a fast-acting poison which was capable of inflicting many painful effects upon the victim, such as intense headaches, nausea, fever, sickness, muscle spasms, and the ultimate deterioration of the foe's bodily functions; meaning that if one of the user's attacks didn't kill the foe, the effects would, as their body was violently dismantled, piece by piece, causing the foe to suffer an agonizing death; and then their corpse would be disintegrated by the scarlet darkness. When faced with opposing elements, the darkness consumed them in order to boost their strength and quantity; making using any sort of elemental based magic are ill-advised against the user; meaning that the user had absolute dominance over the elements. In fact, in this form, not even any Slayers of any element or any Dual-Element Slayer Modes were capable of consuming this Darkness Magic—if they did so, the pain they received from the magic would multiply twentyfold, more often than not completely blowing the opponent straight out of the water.
 * Ragna Triad (黄泉無明長夜流 (ラグナ・トライアド), Raguna Toraido lit. The Underworld's Long Night of Spiritual Darkness Style): The Ragna Triad, also known as the Ultimate Darkness Secret Arts (極暗奥義, Kyokuan Ōgi) is a trio of extremely high-level Darkness Magic spells. They are considered to be the most powerful of darkness-element magics to ever exist—even more powerful than darkness-related Lost Magic or any Darkness Slayer. The power of the spells are such that they are unable to be consumed by any Slayer Magic or manipulated by an outside source no matter what; instead overpowering the foolish magician trying to take their power for their own and devouring their magic in retaliation. They were developed by a Black Wizard during the Human-Dragon War, but how he discovered the triad of spells or created them is unknown; however, soon after the war, the Black Wizard sealed the spells away; hoping that they would never see the light of day again—he wrote down the eternano patterns and instructions in order to cast the spells in an ancient tome, which was buried deep within the earth. When a Sejren Family member activates Corpse Shell, they are capable of utilizing these spells.
 * Ragna Blast (黄泉無明長夜流・冥王下月輪 (ラグナ・ブラスト), Raguna Burasuto lit. The Underworld's Long Night of Spiritual Darkness Style: Demon King's Descending Moon Ring): Ragna Blast is a high-levelled Darkness Magic spell and one of the Ragna Triad of spells. When the user is casting Ragna Blast, the user gathers magical energy from the atmosphere and condenses it upon their blade, adding their own magical power into the mixture, as well as the darkness gathered by the magic, merging the triad of energies and compressing them upon the sword, which causes the blade to become set alight with pitch-black darkness, a darkness which can be likened to that of the abyss. The user forces the darkness to compress into two small wads which are focused on the tip of their blade; from there, the user raises their blade and stabs forward quickly, releasing the darkness in the form of twin enormous pulsating and highly powerful spheres of magical energy that also have the likeness of a comet of immense power, blasting their foe with extreme force twice. This spell has the potential to deal overwhelming damage; as it reacts with the magic origin of the foe and counter-spins it, thus causing their defenses to weaken at the moment of impact; essentially reducing their defenses to zero and inflicting piercing, penetrating damage, unleashing a fiery explosion that deals immense damage; both comets erupt in a powerful surge of darkness that even after the strike, they continue to rise, dissipating into the sky. What makes Ragna Blast so special is that the spell will lock onto the opponent's magical energy, chasing after them and curving in abnormal directions in order to reach the enemy. It will continue to chase them, even to the ends of the earth. The reason for the twin comets is that if the opponent defends themselves against the first blast, the second comet will instantly teleport into its place, and then strike the opponent with its own strength, guaranteeing a strike no matter what the enemy does.
 * Ragna Blade (黄泉無明長夜流・冥王神滅斬 (ラグナ・ブレード), Raguna Bureido lit. The Underworld's Long Night of Spiritual Darkness Style: Demon King's God-Destroying Slash): Ragna Blade is a high-levelled Darkness Magic spell and one of the Ragna Triad of spells. When performing Ragna Blade, the user fuels their magic with negative feelings, fusing eternano and magical power, creating pure darkness, before using the darkness to perfectly replicate the form of an enormous blade composed of negative feelings; the blade is crackling with black energy. Because of this it can only be used in close combat. Ragna Blade is known to be highly sharp and durable, capable of slicing through magical barriers, and its slashes are capable of trailing large amounts of darkness in its wake, which can damage the opponent. The moment that the weapon makes contact with the foe via impaling them, the composition of the weapon is altered to cause additional, smaller blades to protrude from the bladed weapon inside of the foe's body, drastically increasing the number of wounds dealt to the foe. When the Ragna Blade comes into contact with an barricade or anything attempting to defend itself against the spell, the darkness that composes the Ragna Blade momentarily forges itself into sharp fangs, which tears through the so-called "defense" with ease. Only surpassed in power by Ragna Drive, the Ragna Blade's destructive force is enormous. Its effect extends to magic itself, and no being, not even high-level defensive spells can deflect it, although the stronger demons have bodies too big to be destroyed by a single swipe. It puts a likewise huge strain on the caster as well; it requires great amounts of magical energy to be cast (hence it requires amplification for a human caster), and the mere act of keeping the spell active drains the caster's strength tremendously.
 * Ragna Exclamation (黄泉無明長夜流・冥王最力皆合 (ラグナ・エクスクラメーション), Raguna Ekusukuramēhon lit. The Underworld's Long Night of Spiritual Darkness Style: Demon King's Supreme Power, All as One): Ragna Exclamation is the strongest spell of the Ragna Triad; to use it, the user must reach into the very core of their being; their Magic Origin. Once they do, the user pumps all of their demonic energy into the core, essentially overloading it, additionally adding red blood cells to their body, which in turn allows for greater delivery of oxygen and nutrients to their body, essentially increasing the blood flow by forcing more blood through their blood vessels thus increase their potential. When performing the Ragna Exclamation, the user raises their arms, gathering demonic energy within them and forging a link between the realm of the dead and the current plane of existence. From there, the user summons the souls of the fallen Corpse Shell, and they lend the user their power, being manifested into the physical plane, allowing the user to summon Corpse Shell users of all shapes, sizes, types, and abilities from all possible points in time and space; as well as a few Corpse Shell users that do not exist because no timeline ever leads to their creation. From beyond the infinite come infinite Corpse Shells; filling the entire world, an endless army of Corpse Shells. Corpse Shells without a scratch on them, brand-new. Corpse Shells riddled with scars of many fierce battles, old veterans. Corpse Shells that were incomplete, just a bare frame. Corpse Shells that were destroyed, burning in their last moments of magic. Corpse Shells used by other Sejrens of other timelines. Corpse Shells used by people never seen before. Corpse Shells that had no user at all. Corpse Shells used by something inhuman. Corpse Shells that were not even magical. Corpse Shells made of flesh and blood. Huge Corpse Shells. Tiny Corpse Shells. Corpse Shells shaped like beasts. Corpse Shells that had no form at all. Corpse Shells made of liquid. Corpse Shells made of gas. Corpse Shells made of plasma. Corpse Shells made of stars. Corpse Shells that dual-wielded. Corpse Shells drenched with blood. Corpse Shells with two hearts. Corpse Shells that were people. Corpse Shells leading countless soldiers. Corpse Shells riding giant dragons. Corpse Shells that were space battleships. Corpse Shells with swords of light that could kill planets. Corpse Shells that had become gods. Corpse Shells that had fallen to evil. Corpse Shells fused to people. Corpse Shells that had been reborn as people. Corpse Shells of the past. Corpse Shells of the present. Corpse Shells of the future. Corpse Shells that were possible. Corpse Shells that were not possible. Corpse Shells that roamed the void beyond. Once every single Corpse Shell possibility has been manifested, the user performs a simultaneous Ragna Blast/Blade combo with all of their possibilities; the sheer power of which annihilates everything that it touches. The reason that Ragna Exclamation is a 'death and glory' spell is because, by using this spell the user becomes unstable due to their organs and blood vessels slowly tearing and their magical energy going haywire, beginning to suffer physical and mental deterioration, eventually disintegrating. However, their power increases exponentially during the breakdown; which lasts for five minutes. In spite of the fact that this spell is more than powerful enough to kill almost anything, a single use is enough to heavily strain the user's body and completely drain them of their magical power; after casting it, Corpse Shell is cancelled and the user will die.

Notable Users

 * CorpseShellJeanne.jpgJeanne Sejren: As detailed above, Jeanne Sejren was the originator of the Corpse Shell, due to her pact with the demon known as Abyssion. During the final days of the Human-Dragon War, Jeanne used Corpse Shell to cut a wide swathe through the dragon army and end the war on humanity's terms. Her Corpse Shell was one of the two to have a unique appearance—appearing more human-like than the others. However, soon after the end of the war, she was mysterious assassinated –it would later turn out to be by a member of Sin Sector, a subset of the Magic Council- and her blood was used to create further deviations of the Black Art.
 * BlackKnightFull2.jpgCrux Kouga: An experimental homunculus created by the Magic Council under Giselle Mercury's supervision in order to get a pardon for Giselle killing the previous Wizard Saints, using her own DNA and Alphonse's in order to create a "stabilized" Corpse Shell, thus technically making her Tsuruko's sister, as a member of the Sejren Family, she inadvertently inherited the Corpse Curse Brand as well. Hikari would eventually become Crux Kouga due to the seal's tainting influence, among other things. Crux's Corpse Shell looks exactly like the regular version, but it is slightly more powerful, and it seems to reduce his sanity by even more than usual. Crux has an "evolved" Corpse Shell, known as "Black Knight" (黒騎士, Kurokishi).
 * MarisaCorpseShellFull.jpgMarisa Sejren: Marisa Sejren is the current head of the Sejren Family. Having learnt Corpse Shell at an early age, she is said to have mastered the Black Art, so much so that she is one of the few people capable of fighting on-par with a Soul Armour without having one herself with the power of Corpse Shell. Once she discovered Hikari had the Corpse Curse Brand, she taught her a little bit about the magic and how to not be afraid of Abyssion; something that Hikari would completely disregard later on in her life as Crux. Marisa is seemingly immune to Abyssion's corruption, as she has mastered the art of "Clear and Serene", an advanced breathing technique that allows the user to enter a state of tranquility, enabling them to focus their fighting spirit and block out all harmful influences, something she would later teach Tsuruko so that the latter could harness her Deus Machina form without going berserk. Marisa's Corpse Shell is also evolved, being known as """Black Lancer Igalima"" (黒槍騎・イガリマ, Kurosōki Igarima'').
 * Tsuruko Sejren: Tsuruko Sejren is Giselle and Alphonse's daughter, and the supposed inheritor of the Corpse Curse Brand. However, both mother and father absolutely refused to allow Tsuruko to be branded (in fact Giselle killed numerous members of the clan, which is what lead it to die out in the present time)—instead, Star Phoenix, her symbiote, accidently caused a resonance with Abyssion, causing the brand to appear upon Tsuruko's body. Despite this, after Tsuruko was stricken with the Reverse, an incurable disease, and her soul was subsequently implanted into Deus Machina Number Three, the Corpse Curse Brand was eliminated from her body. Original plans for Daybreak would have Tsuruko activating Corpse Shell instead of obtaining the Gaiki Soul Armour. Interestingly, asking the author herself about Daybreak's Soul Armours would reveal that Tsuruko was going to obtain Corpse Shell instead of the Gaiki Armour, which, of course, would have changed pretty much everything about Daybreak. At first, Tsuruko's Corpse Shell would be similar to Crux's in that it would drive her into a berserk state, but eventually, after talking with her family, she would have confronted Abyssion in her mind, her willpower and kindness (or something like that, it would be more likely that she just smashed it into a fine paste) overpowering the demon and destroying it, "purifying" her Corpse Shell and turning it white and blue, as opposed to the normal black and gold. Tsuruko's Corpse Shell would be the most powerful iteration of the magic, as it ran on her own fighting spirit instead of the corrupting influence of a demon, effectively allowing it to last for an indefinite amount of time. This plan was scrapped due to lack of interest, Corpse Shell's general overpowered nature, and the fact that it would cause a lot of plot holes.

Trivia

 * The Corpse Shell was inspired by the Cursed Seal from Naruto and the Devil Gene from the Tekken series.
 * Originally, it was discovered that members of the Sejren Family could "evolve" their Corpse Shell by killing another family member and absorbing their Corpse Shell; and in the early ages after gaining the power, they developed the practice of killing family members in order to become stronger. However, in the current day and age, the family has discontinued this practice, deeming it to be "childish", especially because the city of Luin requires their support and they had to carry out the wishes of Dzerve; they could not die out early.
 * When written purely in kanji, Corpse Shell is written as (骸殻, Gaikaku).