Dementors

"Dementors are among the foulest creatures that walk this earth. They infest the darkest, filthiest places, they glory in decay and despair, they drain peace, hope, and happiness out of the air around them... Get too near a Dementor and every good feeling, every happy memory will be sucked out of you. If it can, the Dementor will feed on you long enough to reduce you to something like itself...soulless and evil. You will be left with nothing but the worst experiences of your life."

- Remus Lupin to Harry Potter.

The Dementors are dark wraith-like creatures that used to work for the Ministry of Magic, to guard the wizard prison Azkaban. Later in the Harry Potter series, they turn against the Ministry and join Voldemort's army. The Dementors are the main antagonists of Prisoner of Azkaban. They do also make an appearance in the beginning of ''Order of the Phoenix. ''In this movie they look slightly different, since their cloaks aren't long. They also do appear very shortly in Deathly Hallows: Part 1, where they chase off the gang of heroes as they try to escape from Dolores Umbridge. Harry blasts them off with a patronus charm.

Appearance
Dementors appear as tall, ominous figures who wear black cloaks, and glide above the ground. Anyone who has seen what is under their hood is in no fit condition to tell what they saw.

19 Years later
When Auror Kingsley Shacklebolt became Minister of Magic, Azkaban stopped using Dementors any longer.

Powers and Abilities
Dementors can drain the happiness and any other postive emotion out of any area. In doing so, they can trap their victims within their own miserable thoughts. Their presence makes any area cold. When they get close enough to their victim, they perform something called a Dementor's Kiss, where they suck their victim's soul out. The only way to beat a Dementor is to cast a partonus, this patronus can be called by thinking of something happy. Happiness is a Dementor's pure weakness. Though they can't be destroyed, they do spawn like fungi, hinting that they die off on their own.

Harry Potter theme park
The Dementors also make an appearance in the Harry Potter and the Forbidden Journey ride at the Harry Potter theme park in Universal Studios in Orlando, Florida. In this ride, the Dementors are trying to suck out the soul of the visitors until they get chased away by Harry Potter himself.