What is the name of the owl-like spirit who owns the great library?

The owl-like spirit who owns the great library is Wan Shi Tong, the Knowledge Spirit in Avatar: The Last Airbender.

Wan Shi Tong’s library is hidden beneath the Si Wong Desert and is described as a repository containing knowledge from across the world. The spirit appears as a gigantic owl and initially permits Team Avatar to search the collection. Sokka uses the library to find information about a solar eclipse that could temporarily deprive Firebenders of their abilities.

Wan Shi Tong is not simply a benevolent librarian. He distrusts humans because they repeatedly use knowledge for warfare and exploitation. When he discovers that Team Avatar wants military intelligence, he becomes hostile and sinks the library deeper into the desert. The group escapes, but Appa is captured outside, setting up the events of “The Desert.”

The wrong options are other spirits or groups: Tui is the Moon Spirit, Koh is the Face Stealer, and Hei Bai is a forest spirit. None owns the great library.