>>96346150
Iroh is 200% MAD that Zhao would resort to such a world-affecting move just for personal victory. Zhao goes through with it anyways, and his army starts advancing. Aang counters by merging with the Ocean Fish, becoming a massive water monster that pushes the Fire Army back and drowns Zhao. Yue, who had been saved by the Moon Fish as a baby, sacrifices her life to restore the Moon Fish to life. She becomes a new moon spirit, and everyone gets their waterbending back. After all the chaos, Katara's mastered enough waterbending to become Aang's teacher as they continue on their travels. Zuko abandons his quest to capture the Avatar, after seeing what such obsession did to Zhao (and getting his ass kicked).
While season one had the main characters travelling to bits of all four nations, season two focuses on the massive Earth Kingdom. With Katara teaching him waterbending, Aang needs to find someone to teach him earthbending. They find that teacher in Toph, a blind girl that uses earthbending "sonar" as her sight. She's from a rich family that coddled her for her blindness, while she was secretly sneaking out to participate in earthbending wrestling. Even after learning how capable and not helpless she was, they insisted on holding her back, so she runs away to join Team Avatar. Her family responds by hiring two mercenaries to find her.