The 'Malleus Maleficarum,' or 'Hammer of Witches,' written by Heinrich Kramer in the fifteenth century, played a pivotal role in shaping early modern European beliefs about witchcraft. It was essentially a guidebook for witch hunters during the European witch hunts, detailing how to identify, interrogate, and punish accused witches. This text fueled the fear of witchcraft in the early modern period, leading to a significant increase in witchcraft trials.