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.

Bob has a great experience in applied magic from being owned by several wizards, as well as innate knowledge of the rules of the supernatural and their current status.

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.

It is implied that Bob had done something to warrant the wrath of Queen Mab, however this has not been expanded on.

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. Events in [|Dead Beat] reveal that Harry is responsible for naming Bob and helping to develop his benign nature. When Harry asks Bob to remember what he can concerning Kemmler, Bob's normally orange eye lights shifted to blue and he attempted to directly influence Harry, for the worse.