* They are used by the Ministry of Magic: The Ministry employs dementors to guard Azkaban prison, a place for imprisoning dark wizards and witches.
* They are used by Voldemort: Voldemort and his Death Eaters utilize dementors as part of their campaign of terror. They are used to intimidate, capture, and even torture those who oppose them.
* They are a threat to the heroes: The heroes, Harry, Ron, and Hermione, encounter dementors throughout the book, facing their terrifying powers and threats.
So, dementors are definitely a significant part of Harry Potter and the Deathly Hallows, both in terms of their role in the larger conflict and their impact on the characters.