"From the first time our ancestors discovered this place, it had already played host to a unique phenomenon in which space itself might overlap in a certain locale. Later, those who came before us would utilize this phenomenon by creating the Serpent's Heart. It would be used to guard secrets, imprison criminals, and worship the great imaginary serpent, Ouroboros.
In the earliest times, this place was called Delphi, the land of snakes. This name did not change even after the arrival of Watatsumi Omikami. Ancient art depicts the scaleless serpent as "Ouroboros," and the coral-adorned serpent as "Orobashi.""

THE FIRST CYCLE,

Was Dainsleif's first and last time being unaware of the curse inlaid upon him. The cruellest of punishments were driven into the Five Sinners and anyone associated with them—— and the sole victim of getting dragged into their punishments was none other than Dainsleif. As the Cataclysm ravaged his home and people, he hardly had the chance to crawl away after suffering a fatal injury during his valiant fight to save as many as he could.He was well aware his curse was different. He could feel the pain of his chest being torn open, the blackhole making home in his flesh; the charred flesh, intricate runes torching his skin; the beastly traits he gradually took on as the years passed; the erosion. It pained him.Revenge driving him to continue on this painful existence, Dainsleif would hunt his brother and his partners-in-crime to the ends of the earth—— and fail. The world was consumed by the Abyss, and in the depths of the Chasm, Dainsleif lost himself to his curse, eroding into nothing more than stardust.

THE SECOND CYCLE,

Dainsleif had expected the eternal slumber that was death; but he instead opened his eyes to find himself once more underneath the cavernous stars of Khaenri'ah. He lived out to adulthood, his awareness and realization of what was happening to him kindled and exploding into a grand flame upon the Cataclysm. Only when this epiphany struck had the God Ouroboros begun to stir in the depths of his being. It came to him in murky, dark dreams during his recovery in the Vourukasha Oasis, midnight and swallow blue flesh glimmering in a cosmic, infinite mess of tangles. It spoke to him of destiny and of the Fate Dainsleif was sealed into within the first breath he drew, of how his brother's abandonment and brainwashing of the Abyss would be the undoing of Teyvat if nothing were to be done about him and the four other Sinners.* * *Once more, Dainsleif suffered through the agony of his chest being ripped open, the expanse of the cosmos sat over his sternum, a milky abyss. Once more, forced to suffer betrayals twice over. Once more, though with a bit more drive, Dainsleif had put in his all to stop his brother.And once more, he failed, and succumbed to the Abyss.

THE THIRD CYCLE,

The Third Descender came upon the Land, only for the Heavenly Principles to tear them apart in a barbaric battle for dominance, tearing holy flesh and bone to create the Gnoses. Their authority was expanding, and both Dainsleif and the dormant Lord of Serpents grew desperate to put a dent in their rapidly growing power.* * *The Gnoses were imbued with the Seven Sovereigns' rightful throne, making Celestia all the more a higher threat. Dainsleif already had his hands full with snuffing out the Five Sinners, but now the Heavenly Principles became too ominous of a threat to be ignored beyond the Cataclysm. The Archons were born with the newfounded Gnoses, and with them things only became more fickle, more complicated.***
They plan to do something with the God of Freedom, yet he cannot tell quite yet, not even in the Fourth Cycle. The enchained, upside down statue, their obsession with his imagery—— to cage the Archon of the Wind surely spells sinister things are afoot.

OUR CURRENT CYCLE,

The Fourth Descenders came upon the land -- and with them, had stirred up the World Formula in ways that neither Ouroboros or his Vessel could ever comprehend. Strange, strange things occured; a Star Being in search of a sibling who has, according to Irminsul, the tree Dainsleif guards so dearly has always existed within Teyvat, said Star Being now leaving massive ripples in the story of Teyvat as piece by piece they break away curses, destruction, pain and suffering to the people ...* * *Dainsleif became curious. Could this be it, could this be the fourth and final cycle he must endure? Before, the Boughkeeper had felt that things had begun to turn for the better with the appearance of the heir of Khaenri'ah, King Irmin's child, who before had never been a variable of the World Formula.

For the first time within his technical thousands of years of existence -- Dainsleif has begun to feel hope, and a dire need to help the Traveller in their cause; not for his own wish to finally be put to rest, but for the fate of Teyvat, too.* * *So much more is at stake than the Traveller realizes—— and Dainsleif aims to make sure he knows the true story, one uninfluenced by the Abyss and its subordinate's whispers.* * *For if even the Traveller succumbs to them—— Teyvat will be doomed once more, and the cycle will begin again.

THOUGH SEEN AS COLD, COMPOSED, AND MELLOW, Dainsleif cannot be written off as something so shallow. One would grow to have such a hard shell to break though if one were to live as long as Dainsleif had, seen what he's seen. Diligent, gentle, eclectic, and endlessly curious, Dainsleif yet remains to be an enigmatic character deeply shrouded in mystery. The Boughkeeper holds a strong sense of justice told by a particular passage in his Albedo miscellany knowing of his practice of Khemia, the alchemy that destroyed his homeland.
HE SEEMS TO HOLD A STRONG RESPECT FOR THOSE WITH A SIMILAR MORAL COMPASS, as he holds a great bought of respect for Diluc, the underdog of Mondstadt, and Jean, who he claims to have done more work for all of Mondstadt in the past thousand or so years of it existing than any other Grandmaster as of yet.DAINSLEIF'S HATRED FOR THE ARCHONS IS A VERY IMPORTANT TRAIT to keep note of with the Boughkeeper's very person—— an understandable hatred to hold, considering the part they played in Khaenri'ah's downfall, and the entirety of Rex Lapis himself. His hatred reaches as far as to conditionally affect his opinion on any deities or mythical beings involving themselves with the Archons, albeit for Ganyu, whom he respects for being so hardworking; Nahida is excluded from this hatred, for 'even he cannot bring himself to hate her'. Whilst he despises the Archons, he has stated specifically he does not hold resentment to a God unless they are loyal to an Archon.

ASIDE FROM DAINSLEIF'S STRONG CURIOSITY, sense of justice, and deep founded, selective respect for those who are allured to duty, the rest of him can only be found in the undertones of his words and glimpses of his past. The Boughkeeper is a somber, sad man. With a body that is eaten away day by day by his curse of immortality, and the constant remembrance of the downfall of his people and homeland, Dainsleif holds a deep homesickness that ails him every waking moment. Endlessly he wanders, recording the stories of anyone, anything he comes across—— for it feels as though it's his duty now, as a man without his king, his people, his home.DAINSLEIF DOESN'T ENJOY THE COMPANY OF PEOPLE TOO MUCH; with the betrayal of Lumine in their long term partnership, he's chosen for the past 400 years to instead wander alone. Though, if one insists, he will hesitantly let them come along. The Twilight Sword doesn't want to admit it, but he does deeply yearn for the company of a warm body travelling next to him once more—— for someone to hear his stories deep into the night, to share a loaf of bread with on cold nights. So he may act aloof, but it is more than apparent for his travel partner that he appreciates and needs them there.

Please note that I use Lumine=Abyss Twin &. Aether=Traveller for the sake of convenience. This does not reflect the lore of any plotline I submit Dainsleif to.

DAINSLEIF IS HEAVILY SHROUDED IN MYSTERY, and chooses purposely to reveal as little about him as he can. Only what we know now was either given to us of his own free volition, or was revealed through the unravelings of our story thus far.THE BOUGHKEEPER USED TO GO BY A DIFFERENT TITLE—— the Twilight Sword. When Khaenri'ah flourished, Dainsleif was honourably given the title of captain of the Royal Knights, and was essentially the righthand to protecting the Royal family of Khaenri'ah. He and five others were deemed as the primary protectors of Khaenri'ah; "The Wise" Hroptatyr, "The Visionary" Vedrfolnir, "Gold" Rhinedottir, "The Foul" Surtalogi, and "Rächer of Solnari" Rerir. Once upon a time, him and the five protectors protected and done great deeds in the golden age of Khaenri'ah; but alas, Vedrfolnir, Dainsleif's elder brother, had been punished by imprisonment and being blinded after divining a fate that left King Irmin infuriated. His elder brother was the first of the five to descend down a path of insanity, driven to obsession with the Abyss. They corrupted the royal line, pushing their number one goal; overthrow the Heavenly Principles and make the Abyss almighty.

THEY MADE THE PRINCESS OF KHAENRI'AH INTO A CONDUIT FOR THE ABYSS, and birthed the events of the Cataclysm. Associated by the Five Sinners, Dainsleif was divinely punished. Deeply hurt by his own blood's betrayal and forced to bear a punishment inflicted upon him and the five other Sinners by Celestia, Dainsleif swore to exact revenge upon him and the four other Sinners.
Initially, this resulted in him and Lumine banding together on their quest to find them all and destroy them before they bring about the end of the world; but, in a twist of Dainsleif's poor luck, Lumine was dragged down with his own brother and turned to their side.THIS ONLY DROVE DAINSLEIF'S DESIRE FOR REVENGE, and now gave him another goal—— save Lumine. For 500 years he's held onto a ring, a goal, and a promise. And for 500 years, he worked towards this goal slowly but surely alone. Aether's arrival was a new variable that changed everything for the Boughkeeper, however. Though he still has not warmed up to the idea of traveling with others again quite yet, Aether had become not only a valuable ally but as well another motive for hanging on until his goals are put to rest, his revenge satisfied.For he, too, understood the pain of watching your beloved sibling spiral into madness.

. . . ouroboros theory &&. backstory pt. ii

There is a reason for the Captain to be revered, worshiped as a God of War. Barely man, he tears through the battlefield with a great-sword in hand, makes blood shower down and paint all in its path a marred red as if the Heavens itself were weeping ichor. To underestimate the First is to meet an idiotic, well-deserved death. No matter how well-trained, it is impossible to emerge from a fight with him victorious, or to draw at a stalemate with no injury.Dainsleif holds no exception to this, Twilight Sword or not.The Serpent's attempt at averting his attention away from the Captain only enrages the Harbinger. As though it were light as a feather, he chucks his claymore with the aim to kill Dainsleif; the blade whistles and hisses from how fast it's flying through the air, a black blur from how it zips across the courtyard. There's a disharmonious symphony buzzing in his ears screaming danger, the death whistle of the sword quickly drawing near the Boughkeeper barely audible to him.It's instantaneous. The crackling crunch, the silence now ringing throughout the courtyard, leaving Dainsleif nauseous from the panic in his head now gone, completely quiet. Warmth seeps through his clothes, quickly followed by pain—— and the lacking weight of his human arm. There's no room for a scream to escape his chapped lips, stumbling forward as his vision doubles, waves, contorts.For the first time out of the five hundred and some change years of facing actual dangers in combat, someone has managed to amputate the Twilight Sword. Mighty serpent, slayer of armers with one sword alone.The punch lands next as he falls to the ground. Dainselif breaks his trance that had compelled him into stillness, and all senses begin to work once more as his body pulses in complete pain. The force of the fist colliding with his face draws blood, and he hacks up more. Dainsleif, trembling with pain, begins to frantically push himself away as he holds the mere stub of his upper bicep. It's so, so much, more than any amount of blood Dainsleif has seen come from his own body, and it's sickening. Two halves of him fight to control the situation as he teeters between keeping his calm, to push through, win this fight—— and pure panic.The Harbinger's taunts are distant to Dainsleif despite their proximity, his body in a haze despite his instincts screaming at every nerve in his body to move, move, move.

SUMMARY

The two most noticeable traits of Dainsleif's curse is that it is a physical disability that weakens the joints consumed by his curse, and that it gradually contorts him into a Primordial Vishap. However, the most significant and altering trait to his curse is the portal sitting in the center of his chest.

MAN-TURNING-BEAST

Dainsleif is being gradually turned into a monster with the special circumstances of his curse. There are a variety of animals pooled into the beast he is contorting to, with the most primary one being a Primordial Vishap; the most noticeable ones were mentioned before in inspirations. Because of this aspect of his Curse, he's begun to grow animalistic features such as claws, a Vishapian tail, fangs, and pointed ears.

BLOODTHIRST

Tying into his MAN-TURNING-BEAST entry, Dainsleif at times craves the taste of blood. It's less of a nurturing thirst (it holds some healing properties, but not enough for him to rely on it) and more-so an urge to satisfy. Dainsleif feels deep guilt over it, especially since the craving can only be satisfied with human blood.

CHEST RIFT &&. PORTALS

The Five Sinners have broken the laws of this world, and for knowing them and being involved with them at some point, Dainsleif was gifted with the cruel irony of turning into a taboo of Teyvat himself. A portal has ripped a hole into his chest, which he has access to and uses to manage inventory. Dainsleif as well has the ability to temporarily create portals or domains. He uses this sparingly and as an ace card, primarily when throwing the Abyss Order off his own trail.

IRMINSUL'S KEEPER

Though Nahida is the embodiment of Irminsul, born from a branch of the Tree of Knowledge itself, Dainsleif maintains the health of Irminsul. Because of this, he has a far higher sensitivity to the Leylines spread all across Teyvat, and is able to pinpoint any tampering of them, especially with the Abyss Order. Any discord within the Leylines directly affect Dainsleif when in a close enough range, and at times can even inflict severe internal pain on him if the damage, contortion, or change of the Leylines is intense enough. Dainsleif as well has Irminsul's collection of knowledge at his fingertips, and is able to recollect information from it at any time.