Mimir ss a giant and one of the Aesir, the god of prophecy, wisdom, ponds, water, and knowledge. He is the son of Ymir. Mimir is the keeper of the Well of Wisdom, the waters of which flow from a spring in the roots of Yggdrasil. He was killed by the Vanir who sent his head back to the Aesir, which Odin saved and perserved. Mimir's head is still capeable of speech and thought, and it allows Odin to drink from the well of wisdom as long as Odin uses his own eye as a cup.