When does The Legend of Korra return?

The Legend of Korra (abbreviated as TLOK) is an American animated fantasy action television series. It is a stand-alone sequel to their previous series, Avatar: The Last Airbender (The Legend of Aang) The series ran for 52 episodes ("chapters") separated into four seasons ("books") from April 14, 2012, to December 19, 2014. The main characters are voiced by Janet Varney, Seychelle Gabriel, David Faustino, P. J. Byrne, J. K. Simmons and Mindy Sterling.