Satan Appearing As A Lovely Maiden

A young man who was walking from Dyserth to Rhyl was overtaken by a lovely young lady dressed in white. She invited conversation, and they walked together awhile talking kindly, but, when they came opposite a pool on the road side she disappeared, in the form of a ball of fire, into the water. All that has reached our days, in corroboration of this tale, is the small pool.

[Owen, Elias. Welsh folk-lore: a collection of the folk-tales and legends of North Wales 1887]