Boggart

A boggart is an amortal shape-shifting non-being that takes on the form of the viewer's worst fear. When facing a boggart, it is best to have someone else along, to try to confuse it, since facing more than one person at once would make it indecisive as to what form it must take, usually a mixed-up amalgam of the victims' fears. Because of their shape-shifting ability, no one knows what a boggart looks like when it is alone, as it instantly changes into your worst fears when you first see it.

The charm that combats a boggart is Riddikulus. The charm requires a strong mind and good concentration. The incantation and wand movement alone will not affect a boggart. The correct way to perform the charm is to push past the fear, and concentrate on something that will make the boggart look amusing. The charm does not, in fact, repel a boggart; it just forces it to assume a shape that the caster will find comical, inspiring laughter, which will defeat a boggart.

Boggarts sometimes do not have the same strength or magic as what they imitate, for example, a Boggart transformed into a Dementor has weaker magic than a real Dementor, according to Lupin, or having a deadly scream as a true Banshee, which would otherwise have slaughtered the entire class. This was partly why he chose to simulate a Dementor attack in Harry's presence to help the boy perfect the use of the Patronus Charm.

Muggles can sometimes see Boggarts, but rarely see them plainly and are often easily convinced that they are a figment of their imagination.

Boggarts were featured in 2006, and changed from person to cobra, then clown, then vomit and Riddikulus and it ends off.