Azula, the former princess of the Fire nation, finds a book in which all the events of team Avatar were written; even the spirits of the North Pole. Something even the reports of the Firenation never spoke about Determined to know what happend the day the moon disappeared, she gets stranded in the North Pole right before winter. This is set after the events of the show. As of 9/2020 , it is also set after the events of the books. Due to them still coming out, I cannot grantee the consistency with the manga adaptation after Imbalance.