Ariana Dumbledore, the sister of Albus and Aberforth Dumbledore, died in the duel between Albus Dumbledore and Gellert Grindelwald, and traveled through time and space. Another omnipotent cold girl from the East replaced her and reappeared in the sight of her brothers.
The girl's name is Corsalia Snake, the only heir to Slytherin's most trusted affiliated family, and the last puppet master in the world.
Before the girl traveled through time and space, she read a book——[Harry Potter]
For the sake of her family, her brother, and her relatives, she 'betrayed' her brother, turned to Voldemort, and became Voldemort's most trusted person.
However, Losa has one biggest drawback - her family and her incurable congenital heart disease.