There were many ways of torture: one of the most atrocious was the research of the so called "devil mark". Inquisitors believed that witches and heretics had an area on their body insensitive to pain (evidence of their dealings with the devil), and to find this invisible satanic mark the tortured body was pierced by hundreds of needels.
Voodoo doll is connectable with this inhuman thing, and moreover it's the only creature that can be tortured (dealing damage to the opponent)
About fire cards, the belief that fire purifies is always rooted in human culture: death sentences were carried out through the inquisitorial bonfire (see Joan of Arc...)