Yue

History
Princess Yue is the sixteen-year-old daughter of Chief Arnook, ruler of the North Pole's Northern Water Tribe. Yue was born with a terrible sickness, and her parents feared she would die. Arnook prayed to the Moon Spirit, and placed her in the Tribe's spirit oasis. The Moon Spirit gifted her with part of its own life force, curing her and turning her hair white as a side-effect. Thus, her parents named her Yue, after the moon.

Upon arriving at the Northern Water Tribe, Sokka was smitten with her at first sight, and the two soon began to arrange meetings. An affection budded between the two, but unfortunately Yue was bound to an arranged marriage to Hahn, a shallow young warrior with more love for high status than for Yue. Sokka and Yue came to realize their love for each other, but Yue could not bear to continue their meetings because they conflicted so with her duty to her tribe. Both of their feelings persisted, and during Admiral Zhao's siege of the Northern Water Tribe, Sokka was ordered by Arnook to act as Yue's bodyguard.

Yue helps Aang to enter the Spirit World by leading him and Katara to the spirit oasis. Later, when Aang has been captured by Zuko, she accompanies Katara and Sokka in tracking the two of them down on Appa. Upon their return to the spirit oasis, they were confronted by Zhao, who fatally struck the Moon Spirit's corporeal form, leaving all Waterbenders powerless without the moon's influence. Yue once again acted to carry out her duty to her tribe, and sacrificed herself in order to give back the life the Moon Spirit had given her when she was a newborn. Her sacrifice came against Sokka's protests, but in the end the young warrior was unable to stop her. Yue died in Sokka's arms, and her spirit appeared before him shortly after, and the two shared a final kiss before she vanished completely.

After the battle beneath Ba Sing Se, Aang met Yue in the Spirit World. She informed him on the damage that had taken place and how to return to his body, and further instructed him to seek out the past four Avatars while avoiding Koh.

Several times following her death, Yue's influence on Sokka returns. In "The Swamp," Sokka, under the place's magical influence, sees a vision of her. The vision of Yue angrily tells Sokka that he failed to protect her, perhaps a manifestation of his fear that she truly felt this way. In "The Desert", Sokka directly refers to the moon as Yue in the intoxicated state brought about by drinking cactus juice. Finally, when Sokka and Suki nearly kiss in "The Serpent's Pass", a waning gibbous moon is visible in the background, alluding to Yue's presence, and Sokka's memories of Yue's death prompt him to act overly protective of Suki.

Trivia

 * Yuè (月) means "Moon" in Chinese.