Perfect!!
10
"Perfect"
Aang arrives in the spirit world and asks a meditating humanoid baboon, Enma, for help. The spirit tells Aang to follow a nearby ball of light, annoyed with Aang for the disruption. The light leads Aang to Avatar Roku. Roku advises for him to see Koh, one of the oldest spirits in existence. He explains that Koh steals the faces of his victims if they show any emotion.
Back in the physical world, the Fire Nation is breaching through the defenses of the Water Tribe. Iroh advises that Zhao finish the attack before the full moon is up. Hahn makes a bold attempt at Zhao but is thrown overboard. Zhao explains to Iroh that when he was a lieutenant under the command of General Shu in the Earth Kingdom, he discovered a hidden library. After looking through nearly every scroll there, he found the identities of the ocean and moon spirits. He plans to kill the spirits to defeat the Water Tribe, despite Iroh's warnings not to challenge them. Meanwhile, Zuko is busy in a frozen wasteland, carrying Aang's body. Taking shelter in a cave, Zuko talks to Aang about his sister, Azula.
In the Spirit World, Aang reaches Koh's lair and comes face-to-face with the face stealer. Koh is angry that a previous incarnation of the Avatar tried to slay him because he stole the face of a woman he loved. Aang questions him about the identities of the moon and ocean spirits. Koh says Tui and La are the names of the spirits; they circle each other in eternal balance for all time. When he mentions Yin and Yan, Aang realizes that the koi fish are the spirits and quickly hides his expression before Koh could steal his face. As he leaves, the Face Stealer declares they will meet again. It is a race against time for Aang to get back and prevent Zhao from eliminating the spirits. He returns to the physical world with the help of a friend, Hei Bai (who hits Enma with a blast of energy). However, he discovers his body is missing and mysteriously becomes a beam of light which shoots over to it, noticed by his friends. Once he is back, Aang uses a gust of air to escape from Zuko by a few feet but didn't make it far. Just then, he is saved by the timely arrival of Katara, Sokka, and Princess Yue on Appa. Zuko and Katara have a rematch but due to the moon being out this time, Katara easily defeats him in a matter of seconds. Aang takes the unconscious Zuko with him, despite some disagreement from Sokka and Katara.
While returning to the oasis, Zhao has already captured the white koi fish. Immediately, the moon glows red, creating a lunar eclipse and color seeps from the world. Immediately, the fighting Waterbenders are rendered helpless. Yue tells the group that she owes the spirits her life for when she was just a baby, she was sick. Her father begged the spirits to save her. On a full moon, Yue's parents placed her in the oasis, where Tui, the moon spirit saved her life, turning her hair snow white as a side effect. Meanwhile, Zhao is making names for himself until Momo jumps on his head. After attempts to get the lemur off, Momo rejoins the group. However, Zhao threatens the white koi, even though Aang cautioned him that removing the moon will affect everybody. When Iroh threatens Zhao against harming the Spirit of the Moon, and Zhao appears to listen, returning the koi. However, Zhao suddenly throws fire at the koi, killing it. The moon vanishes altogether from the sky, leaving complete darkness in the world. Iroh retaliates as promised and Zhao slips away. Iroh and Katara attempt to revive the Moon Spirit, but it is too late. Aang suddenly enters the Avatar state and fuses with the Ocean Spirit, turning into a giant fish-like creature of water. In this state, Aang scours the entire Northern City and massacres the Fire Nation's invasion force, while leaving the citizens of the Water Tribe, who are bowed in worship, unharmed in a manner similar to the Passover. Next, Aang wades out into ocean and wipes out the remainder of the retreating ships.
Meanwhile, Prince Zuko chases down Zhao and his identity as the Blue Spirit (the renegade who released the Avatar from Zhao's imprisonment) is revealed. He and Admiral Zhao fight. Princess Yue, who at birth was saved from death by the moon spirit, sacrifices herself to give the white koi the piece of moon spirit that was inside her. She becomes the reincarnation of Tui, the Moon Spirit, and gives Sokka one final kiss as she fades away and restores the balance of spirits. The moon reappears and La, the Ocean Spirit, dissipates and leaves Aang on a cliff. While returning to the Oasis, La attacks Admiral Zhao and drags him into the sea. Zuko holds his hand out to pull him from harm, but Zhao instead chooses death.
After the battle, Pakku reveals to Katara his intention to head for the South Pole and help rebuild their sister tribe. He assigns Katara as Aang's new Waterbending master. Arnook reveals to Sokka that despite all his attempts, he had known his daughter's destiny from when the spirits gave her life. Zuko and Iroh slip away on a makeshift raft. In the last moments of Book One, the Fire Lord assigns Princess Azula, Zuko's younger sister a mission with the words, "Iroh is a traitor, and your brother Zuko is a failure...I have a task for you."