Star talks to Ponyhead, Janna, Kelly and Starfan13, and they convince her to ditch the party and instead attend another party, where she meets Oskar. A two-hour television film called The Battle for Mewni, which comprises the first four episodes of the third season, premiered on July 15, 2017. As River holds off Meteora, Star and Tom try to reach the sanctuary to revive Marco, but are unable to access it. Pony Head reveals that she knew their plan and used Star to simply prove it, having captured the conversation on video. Meanwhile, Ludo leads his minions through the overgrown beard to find the wand.
Janna and the injured warriors are still hiding when she witnesses Quirky Guy succumb to his wounds. Just as they were about to give up, they suddently find Moon, still suffering from amnesia, making these very pies for the Pie Folk. Before the series was picked up, Nefcy had worked as an artist for Disney's and 's. He also obtains a wand of his own which holds the other half of Star's wand magic. Ludo levitates River into the sky while Marco and the entertainers conspire what to do next.
Marco gets a car ride with Oskar as they pursue Star to get her the wand. Meanwhile, guards have been hot on Pony Head's trail. He also reveals the truth to Star who thanks him for his help. She then hacks into her and discovers her origins: King Shastacan gave her to her as a baby, who then raised her into becoming Heinous. Perhaps it's because I'm disappointed that the creators resorted to the cliche' love triangle trope.
To find out the truth, Moon and Eclipsa secretly infiltrate the Royal Archive, where the entire history of the Butterfly family is held. Star tries to make a replacement statue, but it lacks the scratches and dents that gave the original statue its character. Star begs Marco to use his Quest Buy. During the seance, when Janna falls asleep, Star checks up on Marco with a spy spell, only to find that he and Jackie are having a good time together, which makes her jealous. In the meantime, Eclipsa is put under house arrest.
Although she could easily escape, she is convinced by Janna and the other detention students that she is the Mayor of Detention, and is assigned to help the students out with their needs. When a yarn monster captures the class, Star and Miss Skullnick must work together to save them. The two families compete in Flags, a game where whoever plants their flag atop a dangerous hill full of obstacles gets to look down on the rival family members for a year. When he finds and starts reading Star's journal, Star panics and unleashes her innate magic, which unlocks the door and frees Marco. Marco does not believe Tom has changed but Star decides to go anyway.
Meanwhile, Moon and River are trying to live a quiet life in the woods, until the Maizleys move in next to them. The shape-shifting crow is then revealed as Sebastian, the crow that belongs to Mina, who uses the armored boot to rebuild a full set of armor. Dennis unsuccessfully tries various ways to convince Ludo to come home, but Ludo ultimately comes to realize that he's just not ready to return home yet. Despite some hesitation, Star and Marco go through with it anyway and they seemingly go back to just seeing each other as friends. According to the Butterfly Family book her name should be Festivia, but Eclipsa claims to have never heard of her.
Moon and Meteora then fight and just as Meteora is about to win Eclipsa declares her love for her, which Moon uses as an opportunity to counterattack. Olga's but also because they are throwing a party and building a statue of Princess Turdina. Marco tries to protect Ferguson, who has become the team mascot, from being kidnapped. Realizing how much his brother has done for him, Ludo steals the deed to the castle and continues the reconstruction with Dennis and their other siblings. Star rushes in and reveals that her communication device cannot pick up Moon or Ponyhead's devices, and she declares that they need to return to Mewni. Star becomes suspicious of -for-hire Preston Change-O, who, after every magic trick he does, seems to be something spiritual from the person, and that his hat is becoming longer and longer.
Janna awakens in Meteora's bedroom where Glossaryck tells her that Star is okay. However, afterwards they discover that the pies from the festival were made using Moon's recipe, finally giving them a genuine clue. Tom answers by saying he's giving her space since he was present during Song Day, from which he misinterpreted that she and Marco are in a relationship. Star meanwhile, with help from Eclipsa, deduces Moon to be in the Realm of Magic and heads there. Although they cannot get into the theatre, Tom and Marco watch Mackie lay a beatdown on the movie's security guards. A full grown dark unicorn arrives and attacks them, forcing the original unicorn to use its last ounce of magic to send Star, Marco and Janna away. Meanwhile, Star looks all over the house for a hammer in order to put up a new poster that she just obtained.