Known Reverse Spell

The Reverse Spell (Prior Incantato) was a charm that forced a wand to show an "echo" of the last spell it had performed. Its counter-charm was the Eradication Spell, which removed these images.
The Reverse Spell effect, otherwise known as Priori Incantatem, was an especially rare manifestation of this spell that occurred when two wands with the same core (that was, taken from the same animal) attempted to duel each other. The winner's wand forced the loser's wand to produce "echoes" of the most recent spells performed in reverse order.
==Effects==
===Priori Incantatem===
As dictated by the subtle laws of wands, when a duel occurred between wizards with wand cores harvested from the same creature, simultaneous spell-casting by both parties triggered a rare, powerful effect called Priori Incantatem. Both wands became linked through a single, golden thread. Hundreds of smaller golden beams shot off from this central thread to form a cage around the duellers.
The two wand holders were then forced to compete in a battle of wills by forcing golden beads of light to move along through the beam back towards their opponent. When one wand managed to overcome the other, it forced the losing wand to regurgitate "echoes" of the most recent spells it had cast, in reverse order.
If one of these spells was the Killing Curse, then a ghostly "echo" of the murdered person could emerge from the killer's wand. Such "echoes" retained the "appearance and character" of the deceased person. They were able to hold conversations and could remember the events leading up to and following their deaths. However, these "echoes" were not ghosts, nor were they considered to be returning the deceased person from the dead; indeed, they could only linger on the mortal plane for a few moments before they faded back into the Beyond.
==History==
Amos Diggory cast the Reverse Spell on Harry Potter's wand in the aftermath of the Death Eater attack at the 1994 Quidditch World Cup, in order to determine whether he conjured the Dark Mark over the campsite.
Lord Voldemort was resurrected by Peter Pettigrew using the blood of Harry Potter in the Little Hangleton graveyard on 24 June 1995. A duel ensued between Voldemort and Harry, during which their wands (which both contained feathers from the phoenix Fawkes) became connected, triggering Priori Incantatem. Voldemort's wand was ultimately overcome by Harry's, causing it to release "shadows" of people he had murdered with it: Cedric Diggory, Frank Bryce, Bertha Jorkins, as well as Lily and James Potter.
==Behind the scenes==
*Throughout the film adaptations of the story, there are several instances of two wizards locking spells with one another, presumably for dramatic effect. Although similar to Priori Incantatem, these events did not actually result in a cage of light, nor the release of echoes of past spells.
==Appearances==
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==Notes and references==