At least some content in this article is derived from information featured in: Harry Potter: Magic Awakened & Harry Potter: Puzzles & Spells & Harry Potter: Wizards Unite.
- "Hermione screamed in pain, and Harry turned his wand on her in time to see a jewelled goblet tumbling from her grip. But as it fell, it split, became a shower of goblets, so that a second later, with a great clatter, the floor was covered in identical cups rolling in every direction, the original impossible to discern amongst them."
- — The Gemino Curse used in conjunction with the Flagrante Curse in the Lestrange Vault[src]
The Doubling Charm (Geminio) was a charm used to duplicate an object, creating an exact replica of that object. It could also be used to curse an object into multiplying repeatedly when touched, where it was instead known as the Gemino Curse.
The Doubling Charm was invented by a pair of reclusive twin witches, Helixa and Syna Hyslop, who used it to create duplicates of every item inside their mansion, in which they lived together their whole lives. After their deaths, their relatives finally learned of this practice, discovering two, duplicated sets of hand-written instructions for the spell, one left by each twin.
During the Calamity which affected the Wizarding world in the 2010s, the Gemino Curse affected various objects that were trapped as Foundables by constantly duplicating them, one such example being various Quidditch World Cup trophies. Members of the Statute of Secrecy Task Force had to cancel the spell's effects with the General Counter-Spell which allowed the Foundables to return to their original place in the world.
There was much debate over whether a copy created with the Doubling Charm held the same value as the original, as the two items were impossible to tell apart at first, being identical to one another. However, over time, the copy tended to rot or tarnish more quickly than the original, making it possible to identify eventually. Because of this, the replicas created through this charm are considered to have no value or worth. It is also unknown as to whether or not the Doubling Charm could duplicate living or sentient beings, or if it was able to replicate an object's magical properties. Furthermore, as dictated by the Fundamental Laws of Magic, the Doubling Charm did not affect metaphysical or fundamental entities, such as the soul, as when Hermione Granger used it to create a decoy of Slytherin's Locket, the soul fragment within was not doubled, hence Lord Voldemort's death at the Battle of Hogwarts.
An odd characteristic of the spell, for which a solution was never found, was that only the original caster could stop the multiplication of the object. If the caster did not complete their process of casting, the object would continue multiplying indefinitely, stopping only when the copies began to break down. As such, the Doubling Charm could be used to create a single copy, or multiple, depending on the caster's desires.
This indefinite replication property could be done deliberately as a security measure, where it is known as the Gemino Curse. This caused objects to begin multiplying out of control when touched by an intruder or potential thief, quickly filling up the space with worthless copies of the original object, and trapping or crushing the trespassers.
|Hermione Granger||2 September, 1997||This spell was used by Hermione, creating an exact duplicate of the locket they had stolen from Dolores Umbridge, and giving the replica to the Inquisitor, so that she would not suspect that the locket was missing from her person. Although the spell created an object with exactly the same appearance, it did not duplicate the portion of Tom Riddle's soul that was contained within the locket.|
|Employees at Gringotts Wizarding Bank||Unknown||Employees cast this curse as well as the Flagrante Curse on all of the valuable objects within the Lestrange Vault. When Harry Potter, Ron Weasley, and Hermione Granger entered the vault in order to retrieve Helga Hufflepuff's Cup, the treasures multiplied repeatedly, and nearly crushed the trio after it had grown so large in number, having formed piles that nearly touched the ceiling. The objects proliferated rapidly, the duplicates multiplying themselves, and duplicates resulting from those duplications, ad infinitum.|
|Lottie Turner||2009–2010 school year||Used it to duplicate a portrait of the wizard Harold.|
Latin geminare meaning "to double".
- Harry Potter and the Deathly Hallows (First appearance)
- Harry Potter and the Deathly Hallows: Part 2
- Harry Potter and the Deathly Hallows: Part 2 (video game)
- LEGO Harry Potter: Years 5-7
- Wonderbook: Book of Spells
- Pottermore (Mentioned only)
- Wizarding World (Mentioned only)
- Harry Potter: Wizards Unite
- Harry Potter: Puzzles & Spells
- Harry Potter: Magic Awakened