Book Four: Balance (平衡) is the fourth and final book of The Legend of Korra, spanning a total of thirteen episodes. Set three years after the defeat of the Red Lotus, the book was animated by Studio Mir and the first episode debuted for digital viewing on October 3, 2014. Book Four concluded with the release of the last two episodes on December 19, 2014. The book made its television debut on Nicktoons Network on November 28, 2014, starting with the first three episodes, and also wrapped up on December 19, 2014, with the final four episodes.
Book Three: Change (易) is the title of the third and penultimate book of The Legend of Korra, which will run for a total of thirteen episodes. Set two weeks after the end of Book Two: Spirits, the nomenclature refers to the changes induced by the energy shift of the planet due to Harmonic Convergence and Korra's battle with the Dark Avatar.
As of May 8, 2014, the animation for Book Three has been completed by Studio Mir. Production work for Book Three was officially completed on June 3, 2014. The book debuted with the first three episodes airing on June 27, 2014. On July 24, it was announced that following the airing of "The Terror Within", the remaining five episodes of the book would be moved to online releases, including Nickelodeon's website.
Book Two: Spirits (神靈) is the title of the second book of The Legend of Korra, created by Michael Dante DiMartino and Bryan Konietzko. The nomenclature refers to the focus of the season, a conflict involving the Spirit World.
The book debuted on television on September 13, 2013, though the first episode, "Rebel Spirit", was originally shown to San Diego Comic-Con attendees on July 19, 2013. Spanning fourteen episodes, Book Two concluded on November 22 of the same year. The book also features a two-part special titled "Beginnings", which explores the background of the first Avatar, Wan. It is followed by Book Three: Change.
Book One: Air (气) is the title of the first book of the first season of The Legend of Korra, created by Michael Dante DiMartino and Bryan Konietzko. The nomenclature refers to the Avatar Cycle: water, earth, fire, and air. The primary focus of the season is Korra's attempts to learn airbending from Tenzin while defending Republic City from the Equalist revolt, led by the masked Amon.
The season began on March 24, 2012, with the online airing of "Welcome to Republic City" and "A Leaf in the Wind", and ended at twelve episodes on June 23 of that year with "Skeletons in the Closet" and "Endgame". It was followed by Book Two: Spirits, which began airing on television in September 13, 2013.