The Pewter Heart was a locket that was given to Melinda Warren by her lover Matthew Tate. When Melinda found out that Matthew was a warlock who copied her powers, he revealed to the townspeople that she was a witch. In revenge, Melinda created a curse, the "Warlock Curse" and cursed Matthew in the locket when he came to visit her in the town's jail. Not long after, Melinda was burned at the stake. According to a book that Piper read on Melinda and Matthew, the legend says that the warlock must never be freed or he will destroy the Warren line.