In early Christianity, demonologists often referred to frogs as the ‘Witches Familiar’ or ‘Agent of the Devil’. The fact that frogs resided in swamps and stagnant pools, often dirty and unsanitary places, was used to exemplify the power of consecrated holy water to expel evil spirits and purify sinners. Witches were thought to use frogs and toads in satanic rituals, and to concocted malicious sounding spells and potions from their body parts. Some believe that a witch could be identified by a mark shaped like a toad’s foot secreted on her body or that the image of a toad would be visible in the left eye. Other myths tell of witches extracting toad secretions, or collecting toad saliva for use in flying potions and invisibility spells.
Toads were also popular as poisonous ingredients in potions: “the women-witches of ancient time which killed by poysoning, did much use toads in their confections”. Witches were also believed to control the weather by concocting brews from frogs, toads and snakes, often referred to as “Toad Soup”. Undoubtedly, many experienced illness or death after ingesting or applying some sort of frog-made brew including their toxic secretions. Such folklore and popular mythology was the result of Inquisitional propaganda to eliminate the old Pagan religions and prosecute Witches with charges of heresy during the persecution years.
One of the most widely told myths concerning the toad is that of the “Toad-Stone”, a fabulously jewelled stone that grows inside the toad’s head. This jewelled stone when placed in a ring or a necklace, would heat up or change colour in the presence of poison, thereby protecting the wearer from the dangers of poisoning, a common threat in the Middle Ages.
Source: http://www.controverscial.com/Animals%20and%20Witchcraft_Frog%20and%20Toad.htm
