In a shadowed corner, hunched over a towering stack of Potions texts, Severus Snape was doing his best to ignore all of it. The ball was a chore, a mandatory farce, and the added presence of two other schools only made it worse. He turned a page, his quill scratching a note into the margin.

It was then that a third-year Slytherin, a boy named Mulciber, came barreling around the bookcase. He was grinning, wand raised, chasing after a friend.

It hit Severus square in the chest.

There was a flash of sickly pink light, and a sound like a week-old balloon popping.

The library went silent.

When the light faded, the boy who had been Severus Snape was gone. In his place, sitting in the same chair, hunched over the same Potions texts, was a girl. She wore Severus's too-large robes, her black hair falling in lank curtains around a pale, angular face. Her dark eyes were wide with a horror that had no gender.

Madam Pince's sharp footsteps echoed as she marched over, slippers slapping against the stone. She took one look at the girl in Severus's seat and sniffed.