It's only been a few weeks since the Legend of Korra book 3 finale, but book 4 will premiere October 3.
This is a quick turnaround considering the previous season finished airing August 22 with the last two episodes of book 3.
Book 4 will be called Balance. The video also reveals the title for the fourth chapter of this season will be called "The Calling."
New episodes of book 4 will air every Friday on Nick.com and the Nick app. Nick moved new Korra episodes off the air to be distributed online only in the middle of the third season as ratings declined.
So far, speculation has cast suspicion on a metal clan character introduced in book 3 as a possible villain for book 4. One video shows clips from both book 3 and some that haven't been in the show yet.
This will be the shortest break between seasons for Legend of Korra. The series creators had teased that the final season would air "soon," but no one expected it to be this soon.