Medusa's 18 years old, and she messed up, big time. Her father, for all intents and purpose will be called Papa Gorgon until I figure a good name for him, had enough of her, disowned her, decided that since she had a hard time as child being able to use magic and her most recent screw up means she's a failure to the Gorgon name. For all he cares, she can be somebody else's problem and property. So he decided to sell her as a slave, not caring who buys her, or what they plan to do with her afterwards. Her fate now rests with whoever buys her. Since she's 18, she never had Crona, but Crona still exists in this alternate universe. Crona's gender and if Ragnarock is fused him/her is up to you, but s/he'll still be loyal to the DWMA. Demon Weapons do exist, and Asura still became the first Kishin. Demon Weapons still were created by Arachne, and still hid herself within the Golem after she ran from both Witches and Lord Death. The only thing different here is she tricked some Witches that weren't the brightest and had time powers to go back in time and the rest pretty much went the same way in the original universe.
Everything and everyone is pretty much the same, expect Medusa. Black Star still has his ego, well, I guess it depends on if you do his more developed manga personality. Stein still has a screw in his head, and still dissects things. Lord Death still is the goofball in charge of the DWMA, unless he needs to go back to his old voice, and still Reaper Chops when he's needs to chop an idiot. Spirit still cheated on Kami, and got divorced. Kid still has symmetry on the brain. Blair is still Blair. The sun and the moon still have their faces. Asura's still pants on head crazy, but still locked up in his bag.
In this universe Medusa's personality is way different from the one we know. Does she still have her snake theme? Yes. Is she still as despicable? Not really. She has some of her original personality, but not all of it. Well, maybe a toned version of it if you want to do that. Does she have a problem with killing people? No, but she would rather people not to be stupid enough get her to do that. Like a snake, don't tread on her or she'll strike. Still a smug snake? Yes. In this universe, she probably would never treat Crona the way she did in canon. In this universe, she's a lot like Maka. This Medusa would of liked her parents paying more attention to her, and not always comparing her to Arachne. If it makes it easier, just imagine a marginally nicer Medusa mixed with Maka.
This Medusa sort of looks down on regular humans, due to her father always saying people with magical powers are better. So, she'll say something patronizing every once in a while. Other than that, she's okay with normal people. She has no knowledge of modern human culture. Things like TV, movies, slang words, and pop-culture would make her have face like Stein if you asked him if he could stop dissecting things. She would have no idea what fu*k would mean, or what a blowjob, or titjob is. The only form of sex she knows about is just regular. This would be mainly because of her father. The man had a sneering disgust for anything related to normal humans. Just think about those wizards from Harry Potter that looked down on muggles, and non pure bloods. Good? Now let's move on.
Now that she's being sold, there is going to be changes. She's been conditioned to obey her master, and will obey with fanatical devotion when she's been order. If you told her to take her clothes off and do a cartwheel naked, it would be like a switch flipped in her head. At first she'd try to resist, but would give up and do it. Eventually her conditioning will get to the point she'd beg to serve her owner(s) or maybe even develop romantic feelings for them/her/him, and even before then she can't harm whoever buys her. She can still use her magic, but only if her master and or mistress tells her she can. She may or may not had her assets expanded to make her more desirable. That's up to you, if she does she'll look like herself, but younger and with a bigger chest and butt. If not, she still looks younger but just no expansion. She might still have her usual outfit, or a skimpy snake themed bikini that's basically two straps that only cover her nipples that are still nearly visible, barely covers her pussy and her butt. Or both if you like.
She'll also come with a kit that includes a collar and a leash and potions. The potions can change her, like one of them can do expansions, and one can make her lactate. Here are a couple more besides those you can use. One that will turn her into a cowgirl: horns, bigger breasts that leak milk, and make it where she can only moo. One that will turn her into a bimbo, or one that will have her completely mind controlled. One that'll destroy her mind and leave her as a complete automaton that'll obey. One that can turn her into a catgirl, she'll get cat features, or one that will give her dog features. One that'll increase her libido, her fertility. You can make your own up if you want. And now to the story. She can be anyone's slave. Soul's, Maka's, even Tsubaki's. And make up your reason that got her into this mess.
Medusa just watched as her father signed away her freedom. She was surprised that he would even allow normal humans to buy his daughter. She was hurt that he was doing this, but she was sort of glad that she wouldn't have to see him or her mother again or try to do anything to please them. She thought her mother would do something, but apparently that wasn't going to happen. Come to think of it, Medusa never really liked her parents much. Her mother was more likable than her father, but since her name wasn't Arachne, they wouldn't care. She guessed she knew what was going to happen to Shaula when she messes up to badly. Maybe she'll be bought by the same person that buys her. Next thing she knew was her new owner( s) coming over to her, to pick up the new property. Who was it?