This tale comes from Ireland, a country known for its air of mystic. It was told by the grandfather of a friend, so I suspect it was from around the 1930s or 40s.

The grandfather worked on the estate of an aristocrat. One day the aristocrat encountered a traveling man who was without a place to stay for the night. So the aristocrat (I will call him Stanley) offered him a place to stay in his mansion. Stanley took the stranger back to his home, feed him and offered him drink, before they settled down to a game of cards, using chips as wagers. After some time Stanley dropped a card on the floor. He bent down and picked it up. In doing so he noticed the feet of the stranger. They were hooves, as if from a goat. Stanley sat upright, his visage pale as if he'd seen a ghost. The stranger realised what had happened. He became extremely angry and threw the cards and chips at a mirror, to which they stuck. He them jumped into the frame of the stone fireplace, disappearing into a small crack.

The next the grandfather of my friend was called into the room to clean the mess. He and others tried to remove the chips and cards from the mirror, but they refused to come off. So the mirror was burned. Likewise, he tried to repair the crack in the fireplace, but it refused to be filled; and likely remains as it was to this day.