Work Text:
Medusa's first sin was her birth, depriving Arachne through it of her only child status.
Before that, the attention of their mother had been solely focused on her, as it should have and this change destroyed Arachne's initial sense of self, at the center of the world, forcing her to confront the fact she'd have to contend with others to get the love due to her. For that, she never forgave her little sister.
As long as Medusa was a baby, bullying her behind their mother's back was easy enough; Arachne did it whenever she found herself particularly annoyed by her, which happened often enough. The moment Medusa gained better mobility though, she started fighting back, be it with her little fists, feet, teeth or even bursts of magic she couldn't quite control but which hurt all the same, prickling Arachne like thorns.
The desire to bite back flared but she thought herself too grown-up already to fall to such childish urges. With those new challenges, punishing Medusa's irreverence got more complicated and less satisfying so Arachne opted for ignoring her instead, rather than waste her time anywhere close to this toddler. She would later do the same with their youngest sister but then, that one stayed a mere footnote in comparison to the loathing Medusa inspired her.
They still found themselves in conflict and fought over the years but in more indirect, subtle ways, Arachne undermining Medusa's position in her mother's graces through careful trickeries. It helped that Medusa wasn't an obedient child, making it easy to accuse and sabotage her. Arachne didn't understand why she bothered to rebel, even against their mother. They were better off pleasing her to gather praise and benefits, raising their status in the world through her teachings.
It couldn't last forever of course and soon after Arachne reached adulthood, their mother died. By then, she had learnt all she could from her and set the lofty goal for herself of surpassing their mother's achievements amongst witches, so this passing actually emboldened Arachne to continue on that road.
From that point, her relationship with her sisters changed once again. Now that she aimed for her mother's place, Arache considered it her duty to make sure they finished growing up right, as per her own standards. Because their attitudes and actions reflected on Arachne, she couldn't let them hurt the family name. The opportunity to do what the first Gorgon had failed to achieve in taming Medusa's rebellious spirit appealed very much to her too. In the years following this decision, their relationship worsened and took on a much more violent turn once more since, without surprise, Medusa fought against any order or demand on how she should conduct and carry herself.
If only she had integrated the proper manners Arachne tried to instill in her, she would have been so much more pleasant to look at, turning into a testament of her older sister's good work and taste, but even this was asking too much from Medusa.
Arachne felt both saddened and irritated by the waste in Medusa's refusal to use her assets and embody the beautiful picture she had built for her. That image, so pleasant in her mind, remained out of reach, inachieved. And Arachne had a particular ire towards projects that weren't pushed to completion.
Stalking Medusa's movements also became a necessity after she started leaving their family home more frequently. A deep furor overcame Arachne upon discovering she had been going to some human school behind her back. If Medusa needed to further her education, she could have done it at their house or with a learned witch—one that Arachne had assessed to ensure the quality of her teachings, naturally—but mingling amongst humans in the ways Medusa did, playing mouse and shamefully hiding her identity, rattled Arachne to the point of disgust.
Worst of it, she appeared to have become infatuated with one of the male students doing the same apprenticeship as her. This particular new, more than anything else, caused Arachne to shake with rage. It was unacceptable that her sister would shame herself and her family by engaging with the kind of human that, from the simplest of casual observations, had no value or interest to bring them, unlike the men that Arachne sometimes consorted with and which she always chose while considering how useful they could be to her. She doubted the silly student would know how to properly pleasure her sister's body and imagining Medusa's naked form, in this vile mess, caused her terrible frustration. She hadn't practically raised the damn brat for this.
The boy was a waste of time and a distraction so Arachne did the obvious thing a concerned sister should have done and murdered him.
As she expected, Medusa answered with much resentment and irascibility, even spoiling one of Arachne's socialite parties in her petty rage by threatening the chef and most of the servants into fleeing. She got locked in the dungeon for a few days in punishment and Arachne was satisfied to find her quite deterred from causing more trouble once she finally let her out.
The calm after the storm lasted for a decent while, during which Arachne still unfortunately found herself thinking with bitterness of her sister's body and all the dirty things she might have done with it, unbeknownst to her.
No more than two years later, Arachne discovered that Medusa had started meeting another witch and her stomach turned again. While she'd have accepted a dalliance with a decent number of their peers, a quick check on this one showed she was just no good. Her opinions during assemblies and the attitude she had towards Arachne proved her a lowly witch, a pure nuisance. In all likelihood, Medusa only picked her lovers for the sake of spitting and offending her older sister. Such pettiness had to be answered with utmost severity.
Getting rid of a witch necessitated further subtleties than a mere human but nothing Arachne couldn't achieve. She took care of it then waited for Medusa's reaction, tapping her fan in her palm and thinking with each hit of the joy she would feel for it to strike various parts of Medusa's body instead.
But her little sister didn't come home that day, nor the rest of the week and when Arachne tracked her down, spiders rushing through the land with the haste and fury of a roused army, she realized Medusa's response had simply been to leave without a word.
Arachne's first instinct was to go to her and bring her back, by force and screaming if necessary—preferably, too, for she needed to unleash on the loathsome wench this accumulated rage—however it would have been unbecoming of her to make the effort to go after Medusa. She'd rather have her come back crawling once she had calmed down and realized how ridiculous it was to leave the family home like this. Medusa might have reached adulthood in the recent years but still depended on the place, especially with all her belongings kept inside her personal room.
One month passed and Medusa failed to return. This left Arachne in a frustrating position for deciding how to act next. Her first choice had resulted in no progress but admitting this misshap now by belatedly confronting Medusa didn't please her either.
Like in her youth, she opted to ignore her little sister's fits and focus herself on growing her influence. The best revenge would be to rise and stand above all of witch society while Medusa stayed alone, unable to achieve anything after having fled away from the one who had so wanted to help her, to guide her for her own good. She locked her room, to not be tempted to roam through it and destroy the furnitures in vengeance, having already broken one or two vials when she had first noticed Medusa wasn't coming back. The key of the chamber, she kept close to her chest.
Arachne didn't fully stop observing Medusa from afar, after rearranging her priorities but kept it limited to confirming with her spiders the places she lived in, to be able to visit her once the right time came to rub in the result of Medusa's poor choices.
It only took a few years for it to happen. After the creation of the first demon weapon, Arachne's army evolved to a point where she severely threatened Shinigami and most witches feared her. She could only see further success coming her way and her great mood would be even more improved by a surprise visit to her little sister, whom she knew had been stuck doing shady experiments in rundown, hidden laboratories. Without any proper funding, her possibilities were terribly limited, like Arachne had gathered would happen.
The idea behind this long awaited meeting was to offer a truce, showing herself in a magnanimous light by accepting into her nest the little sister that had so rudely ran away. Arachne's triumph would be at its peak once she had corrected the wrongs done to her that way. Picturing Medusa having to apologize and crawl back to her with her tail between her legs brought the most delicious shiver down her spine.
The sight of the dirty little basement Medusa called her lab highlighted the pathetic of the situation. Arachne felt truly grand in the shabby, cramped place, while exposing her offer calmly and generously. The impertinent but impotent glare of her sister brought her immense joy and the grudging respect she expressed over the creation of the demon weapons nearly brought her to climax; their reunion proved itself to be above all of Arachne's expectations.
Of course, Medusa had to bargain, to try and get some crumbs so she could believe she had the situation in hand, under her control, that she was winning something instead of being bought out. Arachne let her do it, showing her good will by barely fighting the demands and after one hour of back and forth, they had a deal.
"Now that it's all settled, are we good? Come and give me a kiss, sister. This spat has lasted long enough."
She saw Medusa's eyes narrow and her body tense in front of her open arms. The reluctance of her sister appeared all too visible in the light of her inability to decline, now that they had just agreed on something. Indeed, refusing would have been risking throwing away this whole deal and staying in the hole she had finally found a way out from. The distaste born from it felt all the more pleasurable to Arachne, who enjoyed few things more than forcing her to act against her will.
Medusa leaned closer and kissed her cheek quickly, trying to get out of it as fast as possible. Arachne caught her arms to hold her there and make the moment last before kissing her harshly in turn, almost on the lips, sealing their new alliance with her mouth like it had been a spell. And it was more of less it: Medusa belonged to her now, like every other member of her army.
The desire—the instinct—to bite kicked in but Arachne refrained herself. She freed her sister from her grasp instead, briefly petting her hair before letting go.
The extreme disgust on Medusa's face only stung a little. Her sister should have been grateful that Arachne asked No more than this of her. She would have loved to push her into bending the knee and kissing her hand or even to crawl down to the ground and sully her insolent mouth on her feet.
More possessive fantasies gnawed at her and Arachne didn't completely let the idea go, while preparing to leave with her little sister in tow; there would still be time later to satisfy this urge. Once Medusa was settled down at the castle, Arachne could surely find ways to advance on that front, her patience in taming her rewarded at last.
In the worst case scenario, there was Shinigami's fate to account for. When she at last destroyed Lord Death, her superiority would be confirmed for all to see and her sister would have no choice but to submit to her. It'd be her highest pleasure, to reward herself of those combined victories with Medusa's body.