The Battle of the Bands is supposed to be the biggest event of the Hogwarts school year. When {y/n}, Pansy Parkinson and Emmeline Darke discover three identical crimson amulets in a forgotten shop in Knockturn Alley, they think they’ve found the perfect symbol of their friendship. Instead, they awaken something ancient. As every performance draws larger crowds, the amulets quietly drain magic from everyone who listens, feeding on admiration, jealousy and conflict while slowly changing the girls from the inside out. Now, with Hogwarts falling under their spell and the competition reaching its finale, Mattheo Riddle, Regulus Black and the rest of their friends must uncover the truth before the people they love become strangers forever. After all… Some songs are impossible to forget. And some harmonies demand a price.