Mimir
Mimir is a Vanir God, of wisdom and knowledge. He was beheaded during the Aesir-Vanir war, but at the behest of Frigg, Eir preserved his life; as just a head. His sister Vor, also in Asgard, had pleaded that he not be allowed to die; that his knowledge could aid Odin in his rule with true words and intention. Frigg listened, and Mimir became Odin's advisor.
He staying with Odin after the war he acted as an advisor and confident.
He now resides with Odin's wife Frigg in Fensalir, endlessly debating the troubles of the worlds.