As the gang continues on their journey to the North Pole, they stop at the city Omashu, a place Aang remembers from his child-hood for his friend Bumi and its elaborate earth-bending controlled mail system. The group takes advantage of said mail system for fun, but their antics create massive property damage, leading to them being captured by the Royal Guard. The slightly insane King of Omashu realises that Aang is the Avatar, and imprisons Katara and Sokka in living crystal; if Aang wants to free them, he shall have to complete three tasks.