Avatar: The Last Airbender: Season 1, Episode 19

The Siege of the North, Part 1

Zhao begins to launch his attack against the Northern Water Tribe. As the walls of the besieged city begin to fall, the Avatar taps into the spirit world and seeks the help of one of the oldest spirits, in hopes of saving one of the most prominent areas of the world. Can Aang combine forces with the spirits and save the Northern Water Tribe?