A silver hand was presented to Peter Pettigrew by Lord Voldemort at the end of the 1994-1995 school year, to replace his lost right hand. It is a glove like hand, and seems to be composed of metal. This hand has shown strength superior to that of its owner's former hand, capable of crushing a twig to fine dust. It is impervious to the Revulsion Jinx, and possibly any other spells. At first, it seems to be unyielding to Pettigrew's command, but it was designed to strangle its owner if any signs of treason or weakness is shown, as a fail-safe way to ensure Pettigrew will be punished for a second attempt of desertion.
Creation
Peter Pettigrew.
The potion which allowed Lord Voldemort to return needed three important ingredients: bone of a father, flesh of a servant and blood of an enemy. Pettigrew chopped his right hand off in order to supply the second ingredient.
When Voldemort returned, Pettigrew begged for a new hand, as Voldemort has promised him beforehand. His request was honored and Pettigrew was presented with a robust silver hand that was unyielding to a command. Pettigrew tested it out by crushing a twig to fine dust, and was enormously grateful.
Betrayal
During Harry Potter's hunt for Horcruxes, he, alongside Hermione Granger and Ron Weasley were captured and imprisoned at Malfoy Manor, Death Eater headquarters at the time. Following a disturbance from Dobby the house-elf, Disapparating with other prisoners, Pettigrew was ordered to investigate. As he went down the stairs, Harry and Ron tackled him and took his wand. Pettigrew made an attempt to strangle Harry using the silver hand. However, Harry reminded Pettigrew of saving his life four years ago, and Pettigrew released Harry on an unintended moment of mercy. After Pettigrew tried unsuccessfully to undo that moment of mercy, the hand saw its owner wandless and weak, and proceed to strangle him. Despite Harry and Ron's attempts to stop it, it proved to be too powerful to their efforts, and they were forced to watch helplessly as Pettigrew was choked to death.