The Winx Club notices that some of the stars in the sky are disappearing. They determine that the return of Valtor is linked to this strange occurrence. The fairies travel to Lumenia, the Magic Dimension's brightest star and the light source for Stella's home planet of Solaria. Lumenia's queen gives them the power of Cosmix to protect the magical universe's billions of stars. Along the way, the Winx also meet Twinkly; a helpful golden creature who powers the very core of Lumenia.