Prior Incantato is a spell that, if pointed at a wand, can show the last spell performed. It was used by Amos Diggory to learn whose wand had been used to cast the Dark Mark at the 2004-2005 Quidditch World Cup. The Prior Incantato spell could be confused with the Priori Incantatem effect that can be triggered by wands sharing a common core that are forced to duel with each other, but which also can be induced with analytical spells. The spell used to erase the shadow created by the previously used spell (which in turn is produced by this spell) is Deletrius.
Latin prior, "previous", and incantate, "to speak a spell" (past participle incantatum).
Behind the scenes
- In Harry Potter and the Deathly Hallows: Part 1, during the Skirmish at Malfoy Manor in 1998 Bellatrix Lestrange used this spell on Hermione Granger's wand to learn if she used a Stinging Hex on Harry Potter to make him unrecognizable.