It premiered at the Steven Universe panel at San Diego Comic-Con on July 21, 2018, before being released on the Cartoon Network app and website the following day; it was broadcast on television on December 17, 2018.

The episode ends with the introduction of White Diamond, a character theorized about for years by the fans; although she had been hinted at since early in the show's run and her hand could briefly be seen in a flashback in "Your Mother and Mine" earlier in season five, her existence and name had never been officially confirmed prior to the episode, and she was regarded as one of the biggest mysteries of the series.

[2][3][4][5][6] The episode received acclaim from critics, who praised White Diamond's reveal, design, and interaction with Steven, as well as Christine Ebersole's performance as the character; many felt that White Diamond's introduction immediately established her as an impactful and intriguing character, with several reviewers calling her "terrifying".

The two Diamonds also learn that their attack millennia ago in response to Pink's ostensible demise corrupted the remaining Gems on Earth into feral monsters, instead of obliterating them as intended.

Steven, Pearl, Garnet (Estelle), Amethyst (Michaela Dietz), Connie (Grace Rolek), Yellow, and Blue prepare for the journey.

Bismuth (Uzo Aduba), due to her animosity toward the Diamonds, decides to stay on Earth and look after the gems of Peridot and Lapis Lazuli, whose physical forms were destabilized during the battle.

Danny Kilgore, Hilary Florido, and former Adventure Time crew member Tom Herpich wrote and storyboarded the episode, from a story by Kat Morris, Matt Burnett, Ben Levin, Joe Johnston, and series creator and executive producer Rebecca Sugar; Herpich originally worked as a background designer on the show's pilot "The Time Thing", and had re-joined the Steven Universe crew for "Reunited", of which he co-wrote the story.

The existence of White Diamond had been hinted at via background art since early in the series, which led many fans to theorize about her for years.

[2] Sugar stated that the character would be further explored in future episodes and that fans would also learn more about Pink Diamond through White's story.

Although it was acknowledged as a transition episode, the introduction of White Diamond and her dialogue, design, and Christine Ebersole's performance as the character all received high praise.

Her body is perfectly symmetrical, her face is an abstract glowing shape and her voice has a Mary Poppins, sing-song quality to it that dares you to defy her through measured politeness.

Not only is their design both alien and unsettling, but paired with their stature and opened-toed heels (and perfectly polished nails), you know this ain’t the diamond to mess with.