Rayearth's Description

Nova's kinda the dark side of Hikaru. To explain it in more detail, Nova was created when Hikaru left Cefiro after killing Princess Emeraude in the first season. Hikaru hated herself for not being able to do anything to help Princess Emeraude at that time, her feelings were so strong that it created a 'shadow' of herself in Cefiro. But before Nova could go anywhere, Hikaru warped back to Tokyo.

At a certain point, Debonair picked her up and treated Nova as her daughter. In the second season, Nova says Hikaru can only 'play' with her and she hates whatever Hikaru likes and loves whatever Hikaru hates. Nova then goes on a quest to kill Hikaru, she does this because Hikaru hated herself at the moment when Nova was created since Hikaru can't find a way to save Princess Emeraude other than to kill her. In the final episode, Nova was encountered the determined Hikaru who has found out the truth and both of them recombined. Another interesting thing is Nova is part of Hikaru and so is Hikaru part of her. Therefore, that's why she is said to be Hikaru's opposite-self by Clef. If you destroy Nova, part of Hikaru will die too, that's why Lantis was captured by Nova (Lantis didn't want to hurt Hikaru by killing Nova).

Facts about Nova