The episode centers on the reappearance of the Crystal Empire after previously being cursed over a thousand years ago by its tyrant ruler King Sombra before his banishment.

Celestia assigns her student Twilight Sparkle with a test of her ability, and hers alone, to help her brother Prince Shining Armor and his wife Princess Cadance to protect the empire.

Twilight and her friends spread out to ask the citizens about how to protect the empire without Cadance's magic, but find that the Crystal ponies are afflicted with a spell that has erased their memories of anything before King Sombra's reign.

Just then, Cadance's magic shuts down as she collapses in Shining Armor's arms, allowing King Sombra to surround the Empire.

Twilight instructs her friends to keep the fair going while hiding the fake Crystal Heart, while she looks for the real one by herself, assured that this is the test Celestia has given her.

Twilight frets on escaping the trap before realizing the only solution is to have Spike deliver the Heart to Cadance, even though she believes she will fail her test.

[3] At the 2012 San Diego Comic-Con, a preview of "The Failure Song" was shown, which, according to Entertainment Weekly, was "the much-anticipated singing debut for Spike the Dragon".

"[6] The design team decided to make him lack color to describe his evil demeanor and punctuated it using his red eyes and cape.

When changing from one form to another, Sombra bore vague resemblance to Queen Chrysalis with his face, thin body, and legs.

[6] The Crystal Empire's castle, while occupied by Sombra, had sharp steeples and a dark palette to demonstrate its sinister atmosphere.

Despite this, she felt there was an emotional disconnect between some of the plot elements, such as the lack of connection between King Sombra's rule and Twilight and her friends, or on the impact of Celestia's test on the events.

[13] The two-part episode is part of the "Adventures in the Crystal Empire" Region 1 DVD by Shout Factory, which was released on December 4, 2012.