: The Gaang manages to escape just before the building disappears, but Professor Zei chooses to stay behind to continue his research.

: Sokka finds a partially destroyed room detailing "the Fire Nation's darkest day." With the help of a Knowledge Seeker (a fox spirit), he discovers that a solar eclipse will render firebenders powerless.

: The "He Who Knows Ten Thousand Things" spirit who guards the library.

While at a desert oasis, the group meets , an anthropologist from Ba Sing Se obsessed with finding the legendary Wan Shi Tong's Library . Upon finding the buried structure, they encounter its guardian, a massive owl spirit named Wan Shi Tong , who allows them entry only if they contribute new knowledge.

: A scholar whose remains are later seen in the sequel series, The Legend of Korra , implying he never left the library.

: Fox spirits that serve as the library’s librarians.

: Angered by humans using his library for war, Wan Shi Tong decides to sink the library into the Spirit World, trapping everyone inside.