Untransfiguration Spell

The Untransfiguration Spell is the opposite of Transfiguration: it turns a creature or object back to its natural state.

References from the canon

• Professor McGonagall suggested that Harry work on a N.E.W.T. level class in Transfiguration and Untransfiguration if he wanted to become an Auror (OP29).
• "Reparifarge" is suggested by Emeric Switch in A Beginner's Guide to Transfiguration to reverse transfigurations that have gone wrong, such as melding an animal with a piece of furniture (Pm)
• Probably the spell used silently by Remus Lupin and Sirius Black to bring Peter Pettigrew out of his Animagus state in the Shrieking Shack. It created a "flash of blue-white light" from each of their wands (PA19). Sirius said if Scabbers was just a rat, the spell would not harm the creature.
• McGonagall untransfigured Draco Malfoy out of the white ferret state with a "loud snapping noise" but the spell was silent (GF12).