The Protestant Reformation in the sixteenth century fuelled heated debates about the nature and perception of spirits appearing to people. According to Protestant theology, apparitions of spirits were not souls of the dead but either diabolical illusions, natural phenomena, or ‘mere fantasies’ of a deluded mind. Swiss church minister Louis Lavater (1527–1586) emphasized that particularly melancholic people were prone to devilish deceits and thus inclined to imagine ghosts and other spirits. This paper traces the close connection between early modern concepts of melancholy, imagination, and discourses on ghosts in then-normative perspectives before contrasting theological ideals and legal arguments raised in a 1681 Basel trial featuring an allegedly melancholic woman implicated in necromancy. This paper argues that scholarly discussions about imagination and melancholy regarding ghosts in Post-Reformation Switzerland were less concerned with ontological questions about the reality of ghostly phenomena than with possible sinful interactions with ghost, which in turn mirrored ideas about diabolical temptation.