Muggles' Guide to Harry Potter/Magic/Deletrius

Overview
The Deletrius charm ends the display of previously-cast spells from a wand, that was previously triggered by use of the Prior Incantato charm.

Extended Description
In Harry Potter and the Goblet of Fire, the House Elf Winky is found Stunned, holding a wand, shortly after the Dark Mark is cast. The Prior Incantato charm is used to determine that it was, in fact, the wand that was found with Winky that was used to cast the Dark Mark. Once it is confirmed, the Deletrius charm is used to end the display.