The mystery of who the Blue Spirit is has Katara intrigued. Disclaimer - I don't own Avatar: The Last Airbender or Young Justice. This is written for the Green Belt round for Write to Rank 2021 where the goal was to write a story which 1,150 to 1,200 words, is of the action mystery genre, but we're supposed to tell the story in active voice. The mystery is who the Blue Spirit is. Pre Zuko/Katara, but can be read otherwise.