Jiu Ye hung on the tree swaying in the wild wind, pierced by a long spear...
Offering himself as a sacrifice, on the unknown great tree...
——"Poetic Edda"
...
In the distant past of the Nordic World, there once existed a Spring of Wisdom.
It was located in the realm of the Giants, also known as Jotunheim, beside the second root of the World Tree Yggdrasil, guarded by Mimir, thus named.
In the circumstance where none of the gods dared to approach, the king of the Aesir Race sacrificed his right eye, connecting himself to Mimir's Spring because that eye was immersed in the waters of wisdom. Hence, it was equivalent to exchanging sacrifice for incomparable wisdom and insight, allowing the king to glimpse all fate and ancient knowledge.
Then...
This Great God King thus came to know a tremendous secret.
