Damnation (2017)

S3E21 Look Who's Barking

Phoebe experiences a vision of a deadly banshee while updating the Belthazar section of the Book of Shadows, leading her to suspect that Cole is behind it. When the sisters perform a spell to address the situation, it unexpectedly goes wrong and transforms Prue into a dog. After Prue is struck by a car, Phoebe feels immense guilt, triggering the banshee’s wrath and resulting in her own transformation into a banshee.