a boggart gnome

A boggart is a creature in English folklore, either a household spirit or a malevolent genius loci (that is, a geographically-defined spirit) inhabiting fields, marshes, or other topographical features. Other names of this group include bug, bugbear, bugaboo or bug-a-boo, bogey, bogun, bogeyman.

The boggarts inhabiting marshes or holes in the ground are often attributed to serious evildoing, such as the abduction of children.