Cassandra is a character from the 1992 film, The Little Mermaid.
Cassandra was a known eel-tailed sea-witch in the under water world. One time she overheard Lena talking about finding a human prince to marry. She used her magic to conjure up a whirlpool that took unsuspecting Lena to the surface, near a ship, where a prince celebrated his birthday while her two manta ray henchmen Dreyzock and Jhunicka watching her. Later after Lena had fallen for said prince, she came to Cassandra in search of a magic that could turn her to human. Cassandra offered the magic in-change of Lena's voice, with a warning that she would turn to seafoam if the prince marries someone else than her.