The three sisters, Lyrica, Lunasa, and Merlin, are created Poltergeists who were made by Layla Prismriver to have the appearance and personalities of her three older sisters from whom she had been separated. They are technically all the same age since they were presumably created at the same time. They only act out the roles of oldest, middle, and youngest sister based on whichever one they were made to resemble.
Merlin, the second oldest sister of the three, is often viewed as the happy-go-lucky and clueless one of the sisters. She wields the ability to play a trumpet without any physical contact with the instrument. She made her first appearance in Perfect Cherry Blossom as one of the bosses. Her second appearance was in Phantasmagoria of Flower View, which then she was a playable character and a possible opponent.