This chapter focuses on exactly what function the familiar performed in witchcraft narratives and explains the link between it and the diabolical. By emphasising the importance of the familiar spirit and its diabolical associations, it argues that the prevalence of these creatures encourages us to re-evaluate the importance of diabolical ideas to English witchcraft belief. The chapter provides Professor James Sharpe's assertion as its starting point and explores how beliefs about familiars contributed to the diabolical elements of early modern English witchcraft belief. The origins of the familiar spirit remain elusive. One case from 1613 clearly demonstrates the link between the demonic pact and the witch's power to hurt others through a familiar spirit. However, familiars nearly always took the shape of animals. One narrative which highlights the fluidity of descriptions of devils and familiars comes from a pamphlet of 1652.