WHAT’S GOING ON WITH THE MOON?

a thread, because everyone is confused.

Tui, also known as the Moon Spirit, is one of two spirits that reside in the Spirit Oasis at the North Pole within the Northern Water Tribe's capital city, taking the form of a white koi fish with a large black spot on its head.

Together with its counterpart La, Tui was among the first spirits to come to the mortal world, and the pair have kept balance ever since in an "eternal dance" of push and pull. As the Moon Spirit, Tui was the first waterbender and the root of all waterbending.

Thousands of years before the Hundred Year War, Tui and La chose to manifest themselves in the mortal world to benefit mankind and took up residence in an alcove within Agna Qel'a. They lived within this spiritual center of the North Pole and took the form of two koi fish.

When Princess Yue was born, she was gravely ill and on the brink of death, so her father, Chief Arnook, and mother brought her to the Spirit Oasis and prayed for the spirits to save her life.

Tui answered their prayers and saved the princess by passing on some of its own life force. Although Tui had saved Yue, Chief Arnook had a dream that his daughter would one day have to share Tui's place as the Moon Spirit.

Many years later, Admiral Zhao launched a massive attack on the Northern Water Tribe on behalf of the Fire Nation. Determined to make a legend of himself, Zhao lead his personal guard into the royal palace to kill the Moon Spirit.

Tui was captured by Zhao, causing the spiritual equivalent of a lunar eclipse and removing the power of all waterbenders. General Iroh intervened and threatened Zhao that any harm inflicted on the spirit would be unleashed on him tenfold.

Zhao appeared to heed Iroh's warning, releasing Tui back into the water of the Oasis, but the spirit was then abruptly murdered by Zhao with a blast of firebending, much to the horror of Katara, Aang, and Iroh.

Tui's death lead to a lapse in spiritual balance, and waterbending ceased to exist. Taking the slain koi fish into his hands, Iroh realized that Yue held some of Tui's life energy inside her.

Yue then understood she had the choice and responsibility to return this energy to Tui, thus sacrificing herself in order to resurrect it. After Tui had returned to life and the moon was restored, Yue's physical form vanished from Sokka's arms, transcending as a moon spirit.