Boggart

A boggart is a shape-shifting creature that takes on the form of the viewer's worst fear. No one knows what a boggart looks like when it's alone, because as soon as it sees a person, it transforms into what he or she fears the most.

The charm that repels a boggart is: riddikulus. This charm forces the boggart to assume a shape that the spellcaster finds amusing. The thing that finishes a boggart is laughter.

Boggarts are particularly fond of inhabiting certain places that are dark, such as under desks and in wardrobes.

Boggarts were first encountered in Italic textHarry Potter and the Prizoner of AzkabanItalic text in a defence against the dark arts lesson taught by professor Remus Lupin