Gwillion

A creature from the mythology of Wales. It is female, capable of taking the form of a goat. At night it lies in wait for travelers on mountain roads and leads them astray. Sometimes it makes strange sounds similar to a scream, the source of which cannot be determined.

Fresh water is brought to them and they are especially careful that there is no knife or other cutting tool in the corner by the hearth where the Fairy is sitting. "Because trouble often happens to those who don't take care of it."

It's one thing to drive away Fairies on a mountain path, but it's better to welcome them hospitably under the roof of your house. To drive away the gwillions, you should show them an open Bible, a knife or other cutting tool.

The most harmful of the Gwillions is the Mountain Old Woman. She has an outlandish four-cornered hat, ash-colored clothes, an apron thrown over her shoulder, and in her hands either a pot or a wooden vat. 

It is believed that the Old Mountain Woman has stopped appearing since 1800 (at least in South Wales), as she is scared away by the light of the church, and now she lives in coal mines and caves.