In 1233, Pope Gregory IX nailed the last nail to the coffin of a black cat when he declared the black cat the incarnation of the devil. With this statement, Christians tracked down black cats and burned them alive at festivals to punish the incarnation of the devil. The situation was so severe that by the 14th century cats were nearly extinct in some parts of Europe.
Over the next several centuries, superstitious people believed that black cats were disguised by witches. Others claim that black cats can actually turn into witches after being a member of the wizarding world for 7 years. By the 16th and 17th centuries, anyone who owned a black cat was considered a witch and sentenced to death.