Avatar: The Last Airbender (2005)

Season 2: Episode 10

When Aang and his friends find a professor who knows of a library that contains information about the world, Sokka decides to go there to hopefully find some information to use against the Fire Nation. The library is guarded by the knowledge spirit, Wan Shi Tong, who unfortunately doesn't welcome humans into his library, because he believes they only seek information for evil purposes.