A Bwbachold is household spirit or Hobgoblin that performs chores at night while the owners of their dwelling are sleeping. The human owners of the house must leave an offering—usually a cup of ale—by the hearth. The Bwbachold are readily offended, especially by those who refuse to drink with them, and will abandon their home if they feel insulted. They are mischievous and often punish or pull pranks on those they dislike. If angered, they turn malevolent.

Descriptions vary, but typically they are described as ugly, brown-skinned, and covered in hair. In the older stories, they are human-sized. In more recent times, they are small and portrayed as wise. Often, they can turn invisible or possess an ability to shapeshift into animals. They are always either naked or dressed in rags. If a person attempts to present a brownie with clothing or if a person attempts to baptize him, he will leave forever. (Dobby anyone?)