With Moon missing, Star is made acting queen, but struggles with the responsibility. As Meteora heads toward the castle, Star sends Marco to hold her off while she looks for her mother. Marco forms a team composed of himself, Tom, Pony Head, Hekapoo, Talon and Kelly and attempt to trap her, but their plan fails and they are forced to flee with Meteora giving chase. Meanwhile, Star deduces that Moon is in the Realm of Magic and heads there. She eventually finds her mother, who has regained the other one-half of her soul, but suffers from amnesia due to the realm's influence. Star continuously tries to bring her home, but eventually succumbs to the realm's effects herself.
- Eden Sher as Star Butterfly
- Adam McArthur as Marco Diaz
- Rider Strong as Tom Lucitor
- Esmé Bianco as Eclipsa Butterfly
- Jessica Walter as Meteora Butterfly
- Grey DeLisle as Moon Butterfly
- This is the seventh half hour-long episode in the series, following "St. Olga's Reform School for Wayward Princesses", "Storm the Castle", "Bon Bon the Birthday Clown", "Face the Music", "Starcrushed", and "Monster Bash".
- Along with "Conquer", this was the last episode in the series to premiere on Disney XD.
- Star's struggles as acting queen of Mewni share many parallels with her mother's struggles in "Moon the Undaunted".
- July 13, 2018 (Southeast Asia)
- August 20, 2018 (Latin America)
- November 23, 2018 (Portugal)
- January 20, 2019 (Japan)