Star returns to her home dimension of Mewni where she discovers that magic is disappearing throughout the kingdom; Star must dig deep and challenge archnemesis Ludo in an effort to save her family and kingdom.
All the youth of Mewni gather at the ancient Monster Temple to celebrate a new era of monsters and Mewmans living together in peace -- until guests start disappearing.
Star becomes acting Queen and plans for Marco and his warriors to delay Meteora from reaching Castle Butterfly long enough for Star to find Moon and destroy the monster princess.