Final answer:
Heinrich Krämer wrote the 'Malleus Maleficarum,' also known as 'The Witch Hammer,' a guide to identifying and prosecuting witches, which was published in 1487 and significantly impacted the European witch-hunts.
Step-by-step explanation:
Heinrich Krämer, also known under the Latinized name Henricus Institoris, was a German churchman and inquisitor. He is best known for writing 'Malleus Maleficarum' (The Witch Hammer), a notorious treatise on witchcraft. It was first published in Speyer, Germany, in 1487. The book became one of the most influential and widely-cited references on witchcraft, leading to the widespread witch-hunts of the 16th and 17th centuries in Europe. The work reflects the period's beliefs about witches and contributed to the early modern period hysteria surrounding witchcraft.