Avatar: The Last Airbender: Season 3 (Book 3: Fire) (2007)

Description from IMdb:
  In a war-torn world of elemental powers, a young boy reawakens to undertake a dangerous mystic quest to fulfill his destiny as the Avatar, and bring peace to the world.

Media Information:
  Video Codec: x265 10bit
  Audio Codec: Opus
  Container: Matroska (MKV)
  Episodes: 21 (16 files)
  Total Duration: 8:23:22
  Subtitles (BluRay): English (SDH).

Links for more information:
  IMdb Page: https://www.imdb.com/title/tt0417299/
  TVdb Page: https://www.thetvdb.com/series/avatar-the-last-airbender
  Wikipedia: https://en.wikipedia.org/wiki/Avatar:_The_Last_Airbender