Bob

Bob is an air spirit of intellect inhabiting a human skull. He is owned by Harry Dresden, providing him with information and magic lore.

Early history
Bob was bound to the skull by Etienne the Enchanter in France in the Middle Ages. He was later owned by Heinrich Kemmler. After Kemmler's death, the White Council Wardens thought Bob destroyed, but he was in fact taken by Warden Justin DuMorne. DuMorne later left the Wardens, and kept Bob for himself. After DuMorne was killed, Harry Dresden picked up Bob's skull.

Life with Harry Dresden
Bob's skull was picked up by Harry Dresden after the death of Justin DuMorne. It was then that the spirit was named "Bob" by Dresden.