Meeting with the devil willingly was a serious charge, and if proof was gained then it could be deadly. This proved to be the case for the seven who stood trial in 1697. In order to be a witch, according to theory, one had to enter into a pact with the devil. Witnesses declared that they saw many of the accused give themselves to the devil by placing one hand on the crown of their head, and another on the soul of their foot, and offering everything that lay in between to the devil. They would then describe the devil as their Lord, another serious charge.

Some, like Janet Roger, confessed that they had been introduced to the devil by one of the accused, in Rogers' case it was Margaret Lang, who had allegedly performed this service in 1695. The devil often promised things in return, but it was noted that he often failed to deliver. And he rarely offered much, perhaps a new jacket, or that the individual should never want. The limited promises made by the devil tends to reflect the extent of poverty that many of the accused lived in on a daily basis.

The accused were said to have met with the devil in several locations throughout Renfrewshire. More often than not, he was present when a crime was said to have been committed. It was claimed that the devil was often in the witches' company in and around Bargarran house as they plotted the destruction of the laird's daughter. Towards the end of Christian Shaw's suffering, it was alleged that he appeared to her on several occasions. And he would take many forms. Those who confessed remembered that sometimes he resembled a black dog, at other times a black man. He was regularly described as being cold to the touch. Christian Shaw described him variously as a pig, a dark man with bristles, and once as a finely dressed gentleman.