Mummy

"Parvati walked forward, her face set. Snape rounded on her. There was another crack, and where he had stood was a bloodstained, bandaged mummy; its sightless face was turned to Parvati and it began to walk toward her very slowly, dragging its feet, its stiff arms rising —"

- Description of Parvati Patil's boggart.

A mummy is a corpse which has been preserved in some form so as not to decay further if kept in a cool, dry location. Some cultures, most famously the Ancient Egyptians, preserved their dead in this fashion. The Weasley family saw some of these mummies on their 1993 trip to Egypt.

A mummy that has been reanimated in a matter similar to an Inferius was the worst fear of Parvati Patil, and thus her boggart took this form.

Mummy parts could also be used in the manufacture of Belch Powder; 2 drachms of mummy was a required component.

Behind the scenes

 * It is unclear if reanimated mummies actually exist in the wizarding world, or if Parvati had merely been exposed to them via some sort of fictional media. Hypothetically, however, there seems to be no reason a mummified corpse could not be made into an Inferi as easily as any other sort.

Appearances

 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Prisoner of Azkaban (film)
 * Pottermore