Star and Marco face their final conflict.
Star tells Marco that she will destroy the magic which concerns him. She plans to go into the magic realm and use the whispering spell to completely eradicate it. Marco asks Hekapoo what she thinks, as she is made of magic, but she resigns herself to her fate as she thought of magic as being troublesome in general. Moon and Eclipsa are slightly worried over the plan, but ultimately allow it as it is part of Star's destiny. Hekapoo uses her dimensional scissors to open the portal. Marco is given the Royal Magic Wand as he and Star enter hand in hand. When they reach the realm of magic, Marco finds himself slurping up pudding that Glossaryck gave him and suddenly realizes that it is the only thing that keeps them sane inside the realm; knowledge that of course annoys them to no end.
As Star prepares the whispering spell, they spot Tom on top of the dark unicorn. Realizing that the realm of magic has corrupted him, Marco decides to fend him off while Star tries to perform the whispering spell. Her powers fail to work as the realm washes it away, but Moon, Eclipsa and Meteora arrive admitting that Star is right and they need to help. After being fed pudding, the three help Star perform the spell and are accompanied by the spirits of the past Mewni queens. Marco manages to feed pudding into Tom's mouth, but gets pierced by the dark unicorn which he hides. While taking Globgor to the Sanctuary, River and Eddie are captured by Mina who catches on and tries to destroy it. Upon hearing the Butterflys in the well, she jumps in to stop them.
Mina arrives in the realm of magic and prepares to attack the Butterflys, but upon getting distracted from seeing Solaria helping the Butterflys, she is taken out by the dark unicorn. Marco and Tom team up to keep the dark unicorns from harming the Butterflys and they succeed as the realm begins to darken and wither away. Before doing so, Solaria's spirit makes peace with Eclipsa and Meteora. Marco asks Star what the plan is about meeting each other again, but she cannot bring herself to tell him the truth and tells him to go back to Earth. As Glossaryck prepares to "go down with the ship", the Butterflys and Tom return to Mewni, but Star turns around and jumps back into the well. She learns that Marco did not leave and they embrace knowing that no matter what happens, they belong together. A glowing light appears beneath them as everything blacks out.
Star is found unconscious and floating on an alligator in the ruins of the Sanctuary. Moon swims out to her and they witness all the Solarian Soldiers falling and releasing the Mewmans within them. As Buff Frog and the rest of the Monsters wave at them, Star and Moon are reunited with River and see Eclipsa with Globgor and Meteora. They happily embrace, but are interrupted by a returned to normal Mina. Moon offers to help her, but she turns her down; telling her that she has "ideas" and plans to come back, despite having no powers. She calls for people to join her, but only Manfred follows her. Star decides to go check on her friends as she mentions that they no longer have their "cheek thingies", further signifying the lack of magic.
The only people in the infirmary are Pony Head, Seahorse and Rich Pigeon. Star arrives and explains that she destroyed the magic which Pony Head realizes is the reason why Kelly, Jorby, Talon and Janna are gone. Star begs to be given some comfort and Pony Head tells her that Kelly and Jorby are likely back in their realm fighting in another battle, Talon is probably in a tavern somewhere making up stories about himself and while they do not know what happened to the Magic High Commission, it is revealed to the audience that Omnitraxus Prime and Rhombulus (and presumably Hekapoo) perished leaving Sean to eat all their pizza. Tom arrives, having been purposefully ignored by Pony Head, to show Star a magic portal that opened in the sky.
Back on Earth, Britta's Tacos has been completely submerged, leaving Sensei Brantley and Oskar perplexed when asked by reporters. Rafael, Angie and Mariposa arrive to see Marco who is strapped in a stretcher and has completely healed from his wound. As they talk to the paramedics, Janna comes over to check on Marco and is saddened to learn that Star is not with them. She tells him that she considers him her friend and will do anything to help him. She unstraps him and points to the same magic portal that has opened in the sky. To distract the paramedics, Janna drops her heart rate to 0 so that Marco can flee towards the portal.
Marco runs through Echo Creek and comes across Jackie-Lynn and Chloe and borrows the former's skateboard. Star runs through Mewni and passes by a fully reformed Ludo and Dennis playing basketball. The portal begins to shrink as they close in on it. Just as Marco makes it to his side, he trips and falls and the portal explodes. Marco cries, believing he has failed until he looks up and notices dragon cycles flying overhead. He sits up and sees Star standing a few feet from him, panting. Echo Creek and Mewni have merged into one world with modern and fantastic elements fused together. As Mewmans and Humans are surprised and amazed by the sudden fusion in scenery, Star and Marco walk up to one another. They greet each other in relaxed contentment as the northern lights glow above them, ending the series.
- Eden Sher as Star Butterfly
- Adam McArthur as Marco Diaz
- Grey DeLisle as Moon Butterfly / Jackie-Lynn Thomas
- Esmé Bianco as Eclipsa Butterfly
- Amy Sedaris as Mina Loveberry
- Kari Wahlgren as Meteora Butterfly
- Rider Strong as Tom Lucitor
- Abby Elliott as Janna Ordonia
- Zosia Mamet as Hekapoo
- Alan Tudyk as River Butterfly / Ludo
- Jaime Camil as Globgor
- Rhys Darby as Eddie
- Keith David as Glossaryck
- Jenny Slate as Pony Head
- Eddie Perino as Seahorse
- Gary Anthony Williams as Rich Pigeon
- Dana Davis as Kelly
- Dominic Bisignano as Jorby
- Fred Tatasciore as Talon Raventalon
- Josh Sussman as Sean
- Jon Heder as Oskar Greason
- Nick Swardson as Sensei Brantley
- Artt Butler as Rafael Diaz
- Nia Vardalos as Angie Diaz
- Daron Nefcy as StarFan 13
- Kate Higgins as Millhorse
- Jonny Rees as Manfred
- Donna Lynne Champlin as Maude Maizley
- This is the fourteenth and final half hour-long episode in the series.
- Production on this episode was finished on April 12, 2019, roughly one month before its airing.
- This is the first and only episode that does not play the full intro.
- This is the second episode after "Starcrushed" to not feature the ending theme.
- The words of the Whispering Spell are revealed: "Break the bond, tear the fabric, cleave the stone, stop the magic."
- Magic is destroyed, bringing the Age of Magic to an end. As a result...
- Star and her family no longer have cheek marks.
- Mina Loveberry loses her Solarian powers.
- The Solarian Army is destroyed.
- Those that were wounded by Solarian magic are healed.
- Glossaryck, the Magic High Commission, and creatures made of magic are erased from existence.
- All of Star's friends are returned to their respective homes.
- Earth and Mewni are merged into one.
- The reason this happened is because Star and Marco’s strong love for each other responded of what's left of the magic inside their bodies in the realm of magic, merging both dimensions into one.
- While many people have pointed out that the merged world has elements of other dimensions, Daron Nefcy confirmed in a Reddit Q&A that only Earth and Mewni were merged.
- Star is both the first and last character to speak in this series. Although marginally, Marco is the last character to be seen in the series.
- Marco wields the Royal Magic Wand for the second time after "Deep Dive" and is the last person to wield it.
- Meteora apparently gets over her dislike of Marco as after he wields the wand, she begins to giggle excitedly; implying that she has accepted him as part of their family.
- The black marks on Eclipsa's arms are healed.
- Marco's cheek marks appear again after "Booth Buddies".
- Despite Tom no longer having any interest in Star and wanting her to get back together with Marco, Pony Head still does not seem to like having him around her.
- Marco's side of the portal that cleaves Earth and Mewni together is shown to be located outside the Stop & Slurp, where he and Star first became friends in "Star Comes to Earth".
- The title of the episode partly calls back to Glossaryck's line in "Storm the Castle" ("You can cleave something apart, or you can cleave something together") and refers to the two dimensions being "cleaved" into a single dimension.
- Star and Marco’s greeting at the end may be a reference to "Toffee", where they (along with Buff Frog and Moon) exchanged a similar greeting after Star was revealed to be alive.