Avatar Korra fights to keep Republic City safe from the evil forces of both the physical and spiritual worlds. Taking place 70 years after the events of "Avatar: The Last Airbender," this story follows the adventures of the Avatar after Aang - a passionate, rebellious, and fearless teenage girl from the Southern Water Tribe named Korra. With three of the four elements under her belt (Earth, Water, and Fire), Korra seeks to master the final element, Air. Her quest leads her to the epicenter of the modern "Avatar" world, Republic City - a metropolis that is fueled by steampunk technology. It is a virtual melting pot where benders and non-benders from all nations live and thrive. However, Korra discovers that Republic City is plagued by crime as well as a growing anti-bending revolution that threatens to rip it apart. Under the tutelage of Aang's son, Tenzin, Korra begins her airbending training while dealing with the dangers at large. Book Four: Balance is the fourth and final season of the animated television series The Legend of Korra by Michael Dante DiMartino and Bryan Konietzko. It consists of thirteen episodes ("chapters"), all animated by Studio Mir. The episodes are made available on the Nickelodeon website and other online outlets each Friday beginning on October 3, 2014. Critical reception of Book Four, as of the series in general, was positive. Book Four is set three years after the previous season. It deals with Avatar Korra's journey of self-discovery following the physical and psychological injuries she incurred in the fight with Zaheer and with unrest in the Earth Kingdom where Kuvira, formerly a security officer in Suyin Beifong's service, seeks to seize power by military force.