Who was Wan Shi Tong?

Wan Shi Tong is an ancient, wise, and powerful spirit who collects information for his Spirit Library, and thus is the most knowledgeable being among humans and spirits. He never misses an opportunity to learn new facts or boast about his vast intelligence, though he has developed an indifference to studying human technology since leaving the physical world. Although his regular shape is that of a huge black-and-white barn owl, when angered he can assume much more frightening forms.

Long before his encounter with Team Avatar, Wan Shi Tong brought his library from the Spirit World to the physical world. Together with his band of knowledge-seeking foxes, he collected knowledge from all over the world, which he displayed in his library in hopes that humanity would use it to better itself. Although he left his great collection of knowledge available to the mortal world for many years, he eventually became angry at humankind when he observed humans using the library's knowledge solely for the purpose of getting an edge on one another, such as when Zhao came to the library to study about Tui and La's departure of the Spirit World for the human world in order to aid the Fire Nation's invasion of the Northern Water Tribe. Consequently, the owl spirit grew to mistrust humans and banned them from his study.