Barbie and the Diamond Castle is a 2008 directtovideo computeranimated film that was released on September 9, 2008. The film features the voice of Kelly Sheridan, who has voiced Barbie in the CGI Barbie film series. It is the third musical in the series.
The movie begins with Barbie and her best friend Teresa trying to play a song on their guitars when Barbies sister Stacie storms in, angry at her friend Courtney. Barbie decides to tell Stacie the story of two friends named Liana and Alexa, who also get angry at each other.The two best friends live in a hut beside a beautiful garden and plant flowers to make a living. They also share a love of music. One day, they find two heartshaped stones which they make into necklaces to symbolize their friendship, not realizing that they are trinkets from the mythical Diamond Castle. The next day, an old woman gives them a mirror after they share the last of their food with her. The mirror is the hiding place of Melody, an apprentice muse. Melody is on the run from Lydia, one of three muses who lived in the Diamond Castle. Lydia became evil and turned the other two muses to stone, but not before they hid the Castle and left the key with Melody. If Lydia finds the Diamond Castle, all music will end, and with it eventually the world. Liana and Alexa coax a song out of Melody by singing, and Lydias minion, a dragon known as Slyder, locates Melody by her voice. ........
Source: Wikipedia