Barbas, the demon of fear, appears once every thirteen hundred years on Friday the thirteenth. He feeds on young witches for his survival. Entrapped in the Underworld, Barbas must kill thirteen unmarried witches before midnight so that he might be freed to wreak his havoc every day. He kills witches by making their worst fears come to pass and literally scaring them to death.
While in Purgatory, Barbas gained the ability to astral project and used his new ability to plant thoughts in Cole's mind, making him fear his new powers. Eventually he managed to fuel Cole's fear enough that Cole stripped his powers and Barbas absorbed them, allowing Barbas to emerge from Purgatory permanently