"Master ... it is beautiful... thank you... thank you."
"May your loyalty never waver again, Wormtail."
-- Wormtail and Lord Voldemort (GF33)
Given as a replacement after Wormtail sacrificed his right hand so the Dark Lord could be reborn in the graveyard (GF33).
After escaping from Hogwarts on the night of the full moon in Harry's third year, Peter Pettigrew sought out Lord Voldemort, who was basically particle-sized and hiding in Albania. Peter "milked" venom from the fangs of the snake Nagini and mixed it with unicorn blood to keep the Dark Lord alive as a baby-sized creature (GF1, GF34). When Peter encountered Bertha Jorkins, whom he remembered from Hogwarts, he brought her to the Dark Lord so he could interrogate her and discovered from her memories that Death Eater Barty Crouch Jr. had escaped Azkaban with the help of his parents (GF35). Sensing an opportunity to pull something over on Dumbledore, Wormtail and Voldemort came back to Britain and moved into the Riddle House, home of Voldemort's Muggle father and grandparents (GF1).
Barty Crouch Jr was sent to Hogwarts in disguise as Mad-Eye Moody (GF13, GF35). Crouch made sure that Harry would win all the tasks of the Triwizard Tournament, especially the Third Task. But in the end, Cedric Diggory and Harry got to Triwizard Cup at the same time and when they grabbed the portkey it took them straight to the Little Hangleton graveyard near the Riddle House (GF31, GF32).
Wormtail "killed the spare," or Cedric, and kept Harry tied up while he placed "Babymort" in a large cauldron, added a bone from Voldemort's father Tom Riddle Sr., and finally cut off his own right hand and let it fall into the cauldron. He then added some blood from Harry's arm, and from this foul mixture Voldemort rose again with a new body (GF33).
Voldemort let Wormtail suffer terribly and left him bleeding on the ground while calling the other Death Eaters using his Dark Mark. When they were assembled, he told Wormtail that he deserved the pain because he only returned out of fear of his old friends Sirius Black and Remus Lupin, and not out of true loyalty. Then he cast a spell which produced a new silver hand, shining "like a dazzling glove" on his hand. The Dark Lord warned him never to let his loyalty waver again (GF34).
From this point on Wormtail was something of a lowly servant to Snape and the other Death Eaters (HBP2, DH1). He met Harry again in Malfoy Manor and tried immediately to kill him, but when Harry reminded Wormtail of his life debt, Wormtail hesitated only for a moment – and that was enough for the hand created by Voldemort to sense the failing, and the silver hand strangled Wormtail (DH23).
When Goblet of Fire was first released, fans wondered if Wormtail's silver hand would be used to kill his old friend Remus Lupin, since silver is traditionally fatal to werewolves, but the author dismissed that notion on her Official Site (JKR).