Disclaimer: JK Rowling owns HP. My story was inspired by ''Lady Archimides'' by user White Squirrel, but deviates somewhat from the plot of ''the arithmancer''' series (e.g. some characters that die in ''the arithmancer'' verse live in my version and vice versa). Also this story has more Ravenclaw Death Eaters and good Slytherins.
It was May 1998, right after the battle of Hogwarts and Voldemort's defeat. The battle had obviously been won by Harry's side, but not without a great cost. 43 people from the light side lost their lives in the battle, and many more were severely injured.
The survivors with serious injuries were in the medical tent set up by Madam Pomfrey. Some of the other survivors were standing in what remained of the school's courtyard and looked at the devastation that occurred.
What remained of Hogwarts was a sight to behold: many parts of the castle's structure had been brought down in the battle. Turrets were missing from the towers, if they had not been totally destroyed in the battle, such as the astronomy tower during the fatal duel of Hermione Granger and Bellatrix Lestrange. Archways were collapsed and so were the classrooms that they once held up. The parts of the building that still stood were charred, scorched, and still smoking from the spellfire and stained with the rusty red, dried blood of the injured fighters. Bricks and other rubble littered the whole area. Some of the deceased combatants, both good and bad, had been moved to the great hall. But there were still bodies strewn around the debris, lying like limp ragdolls thrown around by a child.
The remaining Hogwarts teachers, Order members, and DA members began casting spells to start repairing the damage, at least the physical aspect. This included the group of students and teachers who had done the arithmantic and runic enchantments on the anchor stones which needed to be enchanted before the ritual to kill Voldemort (designed by Hermione).
The atmosphere had initially been as silent as a graveyard (which it kind of was), as if in memory of the fallen. But someone, perhaps one of the surviving Muggleborns or halfbloods, recast an amplifying charm on an old radio that miraculously managed to survive the battle.
That old radio had actually been used in the battle (of course amplified with a spell), enchanted to play tortured moans and eerie clanking sounds -much like that of the Bloody Baron's eternal chains, but exponentially more terrifying- and a monologue of the wandering, lost spirit of a Death Eater, telling his comrades to turn back while they still can. This had been the idea of the student named Terry (before he had gone to help with the anchor stone enchantments) who had heard of Operation Wandering Soul used in the Vietnam War.
The songs that now played were distinctly Muggle ones, and the ruined courtyard sounded like an impromptu and cruder version of the famous Woodstock concert. Many of the songs were American oldies played by Muggle (and wizards disguised as Muggles) soldiers during wars, like Korea and Vietnam. The atmosphere was far from joyful, of course. Some of the more reserved survivors like Anthony Goldstein and Sue Li protested against this music, but others like Sally Anne Perks and Terry Boot said that the music was fitting.
Septima Vector was one of these survivors who was not too hurt in the battle, so she aided in the clean up as well. As she cast a cleaning charm on a nearby bloodstain, she began to reflect on the past few months.
Even though she had made it out of the battle almost unhurt, she had been tortured almost into insanity a few months ago by the Carrows with the Cruciatus curse when she came out against them during a scuffle. She had hit her head on the stone floors of the castle dungeons when she was tortured, and the resultant head injury had left her struggling with basic math like single variable calculus and arithmancy. She had been teaching arithmancy at Hogwarts and mentoring Rebecca Gamp during her arithmancy mastery as well, but that was currently on hold due to her head injury (Pr. Tinsworth was/had currently been her replacement at Hogwarts but died in battle).
Septima Vector fought back tears thinking about the loss of everything. Some of her former students like Millicent Bulstrode (reformed Death Eater), Marcus Flint, Michael Corner, Hannah Abbott, and Ginny Weasley were lying dead in the great hall. Her colleagues Minerva McGonagall, Filius Flitwick, Sybill Trelawney, Wilhemina Grubbly-Plank, Rubeus Hagrid, Argus Filch, and Irma Pince also lay unmoving among them. Binns had also been ''killed'' (destroyed/exorcised?) by some arcane dark curse during the battle, but he had already been a dead ghost.
She had been relearning math ever since her injury, but it was a slow and difficult process. Being a former Slytherin, ambition was a trait that she prided herself on. She was not going to surrender that easily.
Her thoughts were interrupted by a remark from Terry Boot.
''You know, I would like to do an apprenticeship in arithmancy and become an Unspeakable. I am going back home to the USA for the summer to see my family though,'' Terry spoke again, breaking the brief silence.
"I am not shocked at all, Mr. Boot,'' Septima replied, ''You were one of my top students (despite Hermione and Rebecca) when I taught arithmancy at Hogwarts. I would have been happy to mentor you myself, but I am currently unable to, though I am working to relearn all the math I have lost. I do have some contacts, including ones in the USA, who would be happy to mentor you for your arithmancy mastery," Septima remarked and smirked jokingly, "I am a former Slytherin after all so I do have quite a social network.''
''Thank you so much. That would be awesome!'' Terry replied.
Septima and Terry continued to cast cleaning and repairing spells on the site of the battle scene in silence.
While most would think it was odd to discuss arithmancy and math in the midst of something as tragic as a bloody battle's aftermath, the Ravenclaw and Slytherin (though Septima had almost been a Ravenclaw and Terry almost a Slytherin) found it to be a sense of normality among all the death and suffering.