Dementor

Dementors are a fictional sapient species seen in the Harry Potter franchise.

Nature and Abilities
Dementors are tall cloaked creatures who, although physically tangible, do not appear to be organic, as they are classified with spirits and ghosts. They breed asexually in a manner compared to mushrooms and move by gliding or, for the stronger individuals, outright flying. Dementors are able to suck out people's happy memories when they are near, as well as their magic. If given the chances, Dementors will perform what is known as the "Dementor's Kiss": they put their mouth on their victim's and suck out their soul, destroying it permanently. Dementors are described as "non-beings"; they do not age and cannot be killed with magic or brute force, though they will slowly wither away into nothingness if given no happy memories to feed on for an extended period of time. They can be fended off with the Patronus Charm, which focuses a wizard's happiest memory into a physical shape that appears to repel the creatures.

Place in the Wizarding World
Ever since a large number of Dementors were bred by dark wizard Ekryzdis on Azkaban Island, the descendants of this Dementor colony were used as wardens for the wizarding prison on the island; the wizarding criminals who had committed foulest offences could be sentenced with a Dementor's Kiss. However, the Dementors betrayed their human masters in the second half of the 20th century, turning over to the side of Dark Wizard Lord Voldemort. Though they returned to the Ministry of Magic's service after Voldemort's presumed death in 1981, they quickly flew back to his side when he returned from the dead a dozen years later; after Voldemort was done in for good, the Dementors of Azkaban were exterminated by the new, reformed Ministry.

Inspired
Works of fanfiction have drawn on the books' Dementors to create what can be classified as new creatures:
 * Dementors (Dementors)
 * Dementors (Harry Potter and the Methods of Rationality)