“From its position at the limits of knowing, the monster stands as a warning against exploration of its uncertain demesnes.” -Jeffrey Jerome Cohen, Monster Culture (Seven Theses)
Wan Shi Tong is an ancient spirit who we meet in “The Library” [ATLA, 2.10]. As the creator and caretaker of the Spirit Library, we see Wan Shi Tong’s decisions regarding his library in the physical world as policing the borders of human knowledge.
The owl spirit, in bringing the Spirit Library to the mortal realm, vastly expanded the borders of possible knowledge for humans – knowledge of the spirits and the Spirit World – thereby creating possibilities for the way the physical world could interact with the Spirit World. When he bans humans from his library, he not only polices the borders of human knowledge, but of human interaction with the Spirit World, suggesting that humans no longer should have agency in how they interact with the Spirit World.
Wan Shi Tong, angry at Aang and his friends [ATLA, 2.10]