Eidolon Devil Slayer Magic (滅殺魔王化身魔法, Messatsu Maou Keshin Mahō; lit. "Avatar of a Devil King Annihilation Magic") is a very old and powerful Lost Magic, which is believed to allow mortals to converse with the shapes beyond our world. Though lost to the annuls of history, only dragons and gods are aware of the true extent of this claim. There exists outside our world entities of great unfathomable power, otherworldly to our own that the laws of causality fall before their will. They are antithesis to our reality, yet hunger for it like starved beasts. A horizon of countless eyes and shapeless masses peer through the darkness deep into our world with what might be called curiosity or is it envy? Pressed as they are against the boundaries between space they hear our thoughts and our prayers.
Humans who fear the dark and the unknown cling to their desperate hope of higher powers listening to their cries for help and in the emptiness beyond the heavens, these Great Ones listen. Drawn to these helpless beings, the Great Ones let slip their power through the gaps between the shades of dark, and an unholy communion begins. The first Eidolon Slayers were monstrous, twisted beings whose visage and powers extended far beyond the scope of their ken. Heralds of destruction and chaos their mad ramblings of ascendancy and pinnacle existences made them exceedingly dangerous and formidable foes. Civilizations were toppled as those they conquered were transformed into grotesque mockeries of whatever fallen shape they embodied.
They were a disease, an affliction of death and rebirth that nearly wiped out all of existence. Strangely it was by the hands of each other, for it seems that no one avatar can abide the existence of another and so they were mutually destroyed. The soft utterings of the dark are seductive, for they seek only to bring forth our desires, yet what will be wrought by those ambitions? How will they be changed as our minds become unraveled by the strange machinations of these outsiders? But who can resist such enticing power, when we become free from the laws of casuality? When reality itself shrieks in terror before our will as it infects the world around it realigning nature itself in accordance to our vision? Could you deny yourself this power?
To those who converse with these outsiders they are known simply as the Great Ones. Ancient and utterly alien in both thought and shape these strange entities exist outside the boundaries of space and time as we know it. Their consciousness or perhaps their essence is elevated in an existence far above our comprehension. It is impossible for them to existe conventionally in our world yet they seek it regardless. However they are able to converse with humans who seek audience and from this communion the Eidolon is born. To slip into our reality they require an anchor, a crossing-point, and the body and soul of a human serves as the perfect vessel. In exchange the human is granted immeasurable power, displaying abilities what some might call magic.
In humans terms, this act is, "to mantle the reason" (理由をマントル, riyū o mantoru), for in doing so their very physiology and knowledge changes. They become monstrous but gain otherworldly insight and powerful magical abilities. The nature of these abilities is unique to each Great One, and are not necessarily elemental like those of other Slayers. In fact each Eidolon is entirely unique, the scope of their newfound power and knowledge is their own. The Great One's are not bound by the conventional laws of reality. Their will, the principle of their nature is infectious, it exists as its own state of being and ripples across time and space changing it. As a result they are sensitive or perhaps it is better to say that they are sympathetic to the passions, and desires that permeate through the walls of our world and seep into theirs.
They see our thoughts, feel our imagination, and are thus drawn to individuals whose emotions scream out into the dark abyss. When a Great One comes into contact with a mortal, this event is called Communion (教外別伝, kyougebetsuden). Lacking a physical form, they converse with mortals through their dreams, and in this strange dream world, they elevate the mortal into its netherworld, a sort of space brought about by the thoughts of the Great One. What is spoken and the bargain that is struck is indeterminate, yet the results are nearly always the same, the birth of an Eidolon. For you see, the Great One's are unfathomable in their designs for reality but what is known is that they are indeed very curious, perhaps even obsessed with interfacing with the physical world.
What they derive or what they could possibly obtain from this existence is a mystery yet the details are irrelevant. Power is bestowed, while a responsibility is shouldered, a vision, a philosophy, an ambition. The Eidolon in essence mantles the Great One, receiving their power, the ability to change whatever it is that is in their way, will made manifest. How this works is uncertain. The Communion in the Great One's netherworld should be an impossibility, for their can be no physical exchange or grafting of power. Is it the mind that meets with the Great One, or is the very soul ascending to this consecrated realm? To Mantle The Reason (理由の責任を負担, riyū no sekinin o futan) is the act of calling upon the Great One's power, to allow its unknowing depths slither through the cracks that bound them in the beyond and into our world. It is to see terrifying visions of that-which-is-yet-to-come, or that-which-should-not-be and see them reflected before you.
"Strange is it not? The power in a Curse? It is unlike any natural disaster, for they are indiscriminate in their chaos, blind to the lives they destroy. But a Curse? A Curse has intent. It is a sword of misfortune wielded with purpose. Ponder that for a moment, let it ruminate in your mind. Are you beginning to understand? The magic you wield has purpose, but not ill intent. It is not meant for killing, it is not designed to destroy. A Curse has no other purpose. It exists solely to bring doom upon anything it touches."
"You see it feeds off of our hate, it bathes in our sorrows, and is in pure rapture when it drinks in our misery. This is the nature of the Curse, the core of its power. Magic is neutral, though guided by the wielder it can only ever lean on the axis of life and death, but never be. Curse has no such weakness. That is why you lie there, your pride shattered to pieces, your body broken, and your life slipping away with each passing breath. Let this be my gift to you, a true understanding of magic, may this offer you some measure of solace in your final moments. Now rest, and be at peace, for those you have cherished will soon join you in that blissful slumber." --- Absalon, the Consumed King
The Collected Treatises of King Absalon, Chapter 2
Long have I studied the nature of this power, this corruptive influence. Like oily shadows it seeps into the seams of reality, changing it, almost . . . almost like an infection. I know not its origins, yet its presence grows stronger with each day. I feel as though that a curse is blanketing my people, sapping at their will, devouring their hope. This accursed power is a disease that befouls everything it touches! Even now, the demons that tear my kingdom apart grow increasingly in strength and numbers. A third has already been lost and my generals have informed me, that within a months time, over half of my cities will be subjugated. A king who can not protect his kingdom, is no king at all. I will find a way to win this war. I pray to the gods that they may guide my hand in this dark hour. --- King Abalson's journal, X278
The Collected Treatises of King Absalon, Chapter 3
We were wrong. In less than a fortnight the demons have overrun over half of my kingdom. Time grows ever short, but I've found what I've long since searched for- the source of their strange power! The strength they wield, its origin . . . it is us. The anguish at seeing our loved ones ripped from our grasp, the seething hatred at the monsters who indiscriminately rape and pillage our homes, the overwhelming presence of these emotions. They converge in this imperceptible shape, that cannot be seen nor touched, but it is certainly felt. I feel it, pressing against my mind, grinding against my bones, almost as if it screaming into my ears the answers I so desperately seek. I'm so close, but Im missing something, a nature or an essence that only the demons possess. Tomorrow I will join my soldiers in the field of battle, and I will return one of their ilk and obtain what I desire, no matter the cost. Tonight we join together in silent prayer beseeching the gods for their favor in our most trying time. --- King Abaslon's journal, x278
The Collected Treatises of King Absalon, Chapter 5
The battle was a massacre. My soldiers, brave men and women who had fought by my side for years. Slaugthered! Like animals! The demonic forces were too much, and the bloodshed, the screams, oh god the screams . . . I could not save them. Hallowed by that realization, a fury welled up within me. Liquid fire burned in my veins raging against the injustice of this . . . of this atrocity! So I picked up my blade, stained with the blood of demons and I charged into their midst heedless of the danger. It was in that moment, drowning in rage and despair, that I felt the first tingling of the power. I bathed in their blood, reviled in their fear and, feasted at the table of their gluttony. With defiance in my heart, and hatred in my soul, I roared out cursing them all to oblivion! Awash in those feelings, I felt for the first time an inkling of this . . . accursed power. That was the key. I had to take from them what they had taken from me. I partook of their skin and now it is apart of me. When I face them in battle, I do so in the majesty of their strongest warriors who fell at my feet. I will show them the fear they have inflicted on my people! I will sow the hate in their hearts as they have done for me! In this I shall plunder from their despair, and turn this evil unto my own blade forged in blood and cleave a path to victory! --- King Abalon's journal, x279
The Collected Treatises of King Absalon, Chapter 6
To grasp at the darkness beyond death one's will must be free of doubt and aligned towards a singular unified purpose. For truth is self-evident and I must bear witness if I am to bear its burden. I waged war against the demons, but in the end my kingdom fell. I was forced to abdicate the throne and in the shame of my defeat, I was exiled. Those demons have taken everything from me; my people, my cities, my family. All of it consumed in a baptism of fire. Pain brings wisdom and in my fall I have become very wise. That is when I realized my folly. With the same demonic power wielded by mine enemy, I had battled to save my kingdom. Such is the nature of my failure, such was the height of my naivety. This accursed power can never be used as an instrument to save another. A sword does not become a shield, for war is the design and death its purpose. A soldier fights to save his kingdom, but a King wages war to expand his. This is the path I followed to reclaim my throne. So I pillaged the lands, slew countless demons and took from them all of their strength. Through conquest I took back what was rightfully mine and usurped the false king. When domination and conquest became my nature, I began to purify myself of my weakness, and with that the power of the curse revealed to me at long last. --- Demon King Absalon's journal, x281
The Collected Treatises of King Absalon, Chapter 7
The dark, I know it now, as a warrior knows battle, we have become . . . intimate. Oh yes quite intimate indeed, though not at all like that shallow notion of human love, no this is something . . . deeper. The darkness I speak of, is not a kind mistress, she carves the infinite knowlege of the cosmos on the edge of a jagged blade. To even withstand her excrutiating ministrations one must possess more than just the body of a demon. Acquiring the flesh is a simple feat, one need only slay their numbers until their blood becomes your own. Do you understand? It must be taken, by conquest and battle, such strength must dominated through the crucible of combat. Yet the mind of a demon is ever elusive. It is dare I say it . . . otherworldly to our own.
Not because their way of thinking is so strange to our own, we are in many respects quite similar. There is one key difference however, all demons have a nature if you will that they must remain true. They do not act against this nature, but instead seek to strengthen their will, to align their soul ever closer to the nature that defines them. The human mind is wrought with conflict and doubt, it see's an impossible number of possiblities, and while that is humanities greatest strength, in this it is our greatest weakness. To obtain the mind of a demon, to elevate my mind and transform it into a devil, I will need to divest myself of that which makes me human. Before this terrible war began, my beloved people regarded me as King Abaslon, the Just and Proper King. But . . . well I can always build a new kingdom. Now I must slay and consume the kingdom for which I have sacrificed all that I am. I must take back what I had given. --- Demon King Absalon's journal, x283
The Collected Treatises of King Absalon, Chapter 8
--- Absalon, the Consumed King's journal, x287
The Collected Treatises of King Absalon, The Final Chapter
So very curious . . . this Curse, I know now that my understanding of it was flawed. Consuming the essence of demons did not grant me true insight. Only it was a necessary step towards the axiom of this strange power. A source implies an origin, but that is not the nature of Curse, I do not believe it is native. It is not bound by casual closure. Rather it moves along parallel lines, like little threads if you will that unravel the fabric of reality, but in its passage weaves the frayed edges back together, causing reality to now bear a shape now similar to its own. So if Curse is the thread, am I the needle? Then by whose hand is this story being sewn? Magic is the means to manipulate causality, therefore Curse is a power that defeats these laws. Its nature is paracausal, and paradoxically it both consumes and repels magic and by extension our reality. No mere mortal can wield this power, they would be consumed, their mind devoured, their soul torn asunder. To withstand the might of Curse, one must be a devil in both mind and body.
--- Absalon, the Consumed King to Zeref, as scribed by an Etherios in x422
- I stood at a great precipice, a ledge of dread serving as my foothold, while black and blood red stars illuminated the heavens above me. Perception was distorted, irrational even. My senses did not work as they were designed to, for I could feel my mind struggle to process what it was experiencing. Then as if a great darkness swallowed the dark skies itself, a shape took hold. Tears of blood flowed freely, my vision fractured into a kaleidoscope of different perspectives. The swirling nebula of colors I could not yet perceive spat blotches across my field of sight. I could . . . no it was more like . . . I know you?
- The world shifts, no, shatters and reforms countless times in the span of a moment, I could see the conflux of time as it twisted and bent towards a singular point. Pain engulfs my being, but it is comforting, a confirmation of my own existence. My mind ripples as sensation filters through the cracks of my frayed mind, tiny streams of . . . flesh and bone sew together forming a body . . . mine? The sudden existence of having a body causes me to lurch over gasping deep breathes for air . . . but is this air, and if not then why do I draw breath? I gaze upward and find myself before a deep and powerful presence, and to know it was to grasp the infinite.
- Its mind touched at everything and nothing, its principle simply being the foundation for this existence. I knew not how I could sense it, let alone perceive what was happening but I knew that the laws that governed this reality were at once being made in accordance to . Before me was a god in all but name, I could feel how ancient its mind was. The rise and fall of the entire history of our world, was a foot note on a single page of the infinite tome of its memory. Where was this? It was a realm unto itself, a throneworld from where it could gaze upon our own. In this nethersphere my existence struggled to be, and before this Great One, I was so verily insignificant. The concept of my own existence . . . of me . . . was dwarfed, yet I was not yet snuffed out. Interesting. How very interesting. --- Demon King Absalon
Communion (教外別伝, kyougebetsuden), is an event by which the heavens themselves are shifted, the darkness between the void cracks and the mind of a Great One descends. The phenomena was once considered an astrological anomaly occurring periodically throughout history, due to the luminosity of nearby stars seemingly upending as a void seemingly charted its way across our skies. Oft times the tides all across a country would recede, and the moon itself would fade from sight as though shifting out of phase. Each event is different as is presumably the Great One that reaches out, but there is an accord of some kind, a bonding perhaps. The details of which remain shrouded but the aftermath, that is the only measurement by which history known only to Dragons, Gods and Devils have been able to grasp why a mortal suddenly obtains powers that defy existence itself.
Unbeknownst to all but the mortal who called the Geat One, it is a very strange, unseemly time where the laws of reality act less like laws and more like . . . suggestions. In this realm hidden between the spaces of dimensions, where thoughts and dreams echo out to infinity, where perception becomes causality, a Great One converses with a mortal. The very act of communion creates a shared space where the Great One tentatively resides, or perhaps it is a mere projection of their unfathomable thoughts. Regardless this extra-planar mindscape serves as a bridge between the Great One and the mortal. It serves as a sanctuary and bastion that allows the Great One to presumably peer ever more closely into our reality, and more easily affect changes as the power granted by the mortal shapes the world around them.