Nyctalgia-Tom Riddle

Elaria Rosier is the daughter of Vinda Rosier, Gellert Grindelwald's most loyal follower and one of his most trusted allies, Vinda survived past Grindelwald's downfall, she was captured by the International Confederation of Wizards or various European magical authorities. Considering the scale of Grindelwald's crimes, his most trusted followers would have been treated as highly dangerous criminals, likely facing severe punishment.
Unlike Voldemort's followers, who were sometimes able to plead innocence or lie their way out of Azkaban, Grindelwald's followers were more notorious and public in their actions. She may have been sentenced to a lifetime in Nurmengard, the very prison that Grindelwald himself built. Alternatively, depending on what they could pin on her and the severity of her crimes, she could have been executed as an example to prevent future dark uprisings, although vinda didn't leave without leaving a mess behind, this being her two children Elaria and Alistair. That both attended Hogwarts through their first 4 years before vinda knew she couldn't outrun the ministry she sent them both to Russia without a trace, with the ultimate goal they would both have more power than what they could contain. Elaria being Slytherin's golden girl before her disappearance and Alistair was Slytherin's troublemaker before the downfall of the rosier family. 7th year at Hogwarts both come back, but things will not be the same, upon finding out both of the dark lords son constantly meddle in their affairs and their former friend's betrayal, chaos is unleashed