Rachel Argosy was a late bloomer in terms of her mutant nature not manifesting until she was older, due to her having meningitis as as a child. A high school teacher in Two Rorks, Maine. Argosy was fired after the school received complaints about her being a mutant.
She sought to use her powers to make the school board's leader Harry Sharp to change his mind but accidentally caused his death from a heart attack. Quicksliver and Multiple Man of the government sponsored X-Factor were sent to apprehend her.
Despite her best attempts to convince them otherwise, Argosy was found guilty of causing Sharp's death and sentenced to a lengthy prison where she presumeably remains to this day.
She is one of the 2% of mutants to retain their powers post-Decimation.
Rachel is able to use the music she creates when playing musical instruments to warp reality with variety of effects such as producing hallucinations, mind control, manipulating emotions, and flight. Rhapsody also has blue skin. She is a talented violinist and flute player. She generally uses these instruments to harness her powers.