Gone with the Witches

Christy has now managed to convince Billie that the charmed ones are too self obsessed to help the 'greater good' so when Paige, Phoebe and Piper attempt to involve the rest of the magical community, Christie and Billie turn all the leprechauns and other creatures against the girls. Christie and Billie then directly attack the Charmed ones who attempt to escape to magic school but find that it has been blocked from them and so are sent to the underworld