‘The charm that repels a Boggart is simple, yet it requires force of mind. You see, the thing that really finishes a Boggart is laughter. What you need to do is force it to assume a shape that you find amusing.'
The Boggart can appear in different forms: Professor Snape, a mummy, a hand, a spider, a banshee.
Cast Riddikulus properly to transform the Boggart into a more laughable shape.
The extra information can only be accessed if the Boggart appears in the shape of a mummy. Cast Riddikulus and then click on the unravelled body. (If you don't get a mummy, refresh the page until you do.)