In the year 1233, Pope Gregory IX issued a papal bull titled Vox in Rama (A Voice in Rama), which condemned a German heresy known as Luciferian, a form of devil worship.
In a way, the bull marked the beginning of sustained efforts by the Catholic Church to demonize perceived heretics and link them with devil worship. The same year the bull was issued, an inquisitor named Conrad von Marburg reported he had uncovered a satanic cult that worshiped a diabolic black cat.
However, a papal official sent to Marburg later warned Pope Gregory IX that von Marburg’s had used torture or threats thereof to extract many of the confessions he used as evidence of the cult.
The cult was described as having bizarre initiation rites, which involved the initiate being approached by a toad (and sometimes other animals such as geese or ducks), followed by an emaciated pale man who would make the initiate forget all about the Catholic faith. Later, the ceremony involved the appearance of a black cat, which would walk backwards with its tail erect.
The initiate and the leader of the sect would kiss the cat on the buttocks. This would complete the ritual, after which the sect would engage in an orgy and be visited by something described as half-man half-cat (apparently the devil).
An interesting fact about the bull is the prominent place of the black cat in the initiation ritual, and the description of the devil as having a half-feline form. Although the pope gave no direct order to exterminate cats, but rather described their use in satanic rituals, the bull led to the widespread persecution on cats in Western Europe.
Vox in Rama may be the source of the modern association of witches with black cats.