The great serpent is an ancient ouroboros symbol of the eternal and cyclic nature of time. Its usage predates the wheel.
Aes Sedai wear a gold ring with this symbol on the finger and hand of their choice, if they choose to wear it at all, in addition to their shawl to indicate their position.
Accepted wear this ring on their third finger of their left hand.
Background[]
The great serpent is used as end-of-chapter icons as well as in the maps of the books.