Golden Egg

From Hpwiki

Harry Potter uses a golden egg to solve the mystery of what the Second Task will be in the Tri-Wizard Tournament during Harry Potter and the Goblet of Fire. When told by Cedric Diggory to take a bath with the egg, he takes it into the Prefects' Bathroom, where Moaning Myrtle suggests he put it under the water. When he listens to it while underwater, he figures out that the mer-folk will take something from him and he'll have an hour to get it back.

"Golden Egg" is also a music piece on the Harry Potter and the Goblet of Fire Soundtrack.