Princess Yue was a princess of the Northern Water Tribe, daughter of Chief Arnook, as well as one of the latter's advisors. After the death of Tui during the Siege of the North, she sacrificed her life to replace it and shared its position as the Moon Spirit.
Yue appears in a vision Sokka see when he and Team Avatar are lost in the Swamps, where she blames Sokka for failing to protect her during the Siege of the North. Sokka later reasons that he was hallucinating. However, she, Kya and Toph are seen when the Fog Swamp as the water tribesmen here state that no one is ever really gone.
In "The Desert," Sokka is drugged on cactus juice hallucinogens. Aang mistakes a cloud for Appa (who was stolen by Sandbenders earlier. She said that Yue doesn't need Appa because she flies on her own as the Moon Spirit.
In "The Serpent's Pass," Sokka and Suki are later reunited when he and Team Avatar are on their way to Ba Sing Se. He starts acting overprotective of Suki when she offers to protect Team Avatar and two refugees down the Serpent's pass. Suki confronted Sokka, who revealed that he failed to protect someone at the North and that is why he is acting protective of her. As the two kiss, Sokka stops himself out of respect for Yue because he feels uncomfortable kissing her in front of the Moon.
