The Duplication Charm

A charm used to duplicate an object to create an exact replica nearly impossible to tell apart from the original. Hermione uses the charm to not arouse suspicion when she, Harry and Ron take Slytherin's locket from Umbridge. The spell could also could be used as a curse using the incantation Gemino, known as the the Gemino Curse, where an object when touched would replicate ad infinitum, filling a space and crushing any intruder or trespasser under the weight of replicated items - this precaution was placed on the treasure in Bellatrix Lestrange's Gringotts vault.