His function depends on which source you read, like many of the Norse god/goddesses. In one myth, he is the wisest of the Vanir and sent to the Aesir as a hostage in a peace making process. In another tradition, he is created when the Aesir and Vanir mix together their spit in a peace making ritual. He is the wisest being. Later on, he is killed by dwarves who make his blood into mead, the mead of poetry.