The season's antagonists are the "Red Lotus", a group of dangerous anarchists led by the new airbender Zaheer who wants to overthrow the world's governments and the Avatar.

[13] The sand shark from which Korra and Asami flee in episode 10 is based on the sarcastic fringehead, a small fish found in the Pacific.

[10] Book Three introduced many new characters that would recur until the end of the series, including the extended Beifong family and Jinora's romantic interest, the orphaned thief Kai, named after writer Josh Hamilton's son.

[11] Henry Rollins expressed interest for auditioning for the role of the season's main antagonist Zaheer, calling Konietzko and DiMartino from a tour to pose questions about the character.

[10] The writers considered and rejected including a flashback to the Red Lotus's attempted kidnapping of Korra as a child, and also cut a scene of Asami and Lin sneaking into the airship in episode 4.

[10] In addition, they began to allude to the possibility of a mutual attraction between the two that would result in them becoming romantically linked in the final moments of the series.

And, Hoffman wrote, by showing Korra to suffer from "full-on depression" at the end of the third season, and devoting much of the fourth to her recovery, the series helped normalize mental health issues, a theme generally unaddressed in children's television, which made them less oppressive for the viewers.