Golden egg

The golden egg was a magical device and the goal of the first task of the Tri-Wizard Tournament. It was about the size of a regular dragon egg and placed among the female dragons' eggs, where the Viktor Krum, Fleur Delacour, Cedric Diggory, and Harry Potter had to retrieve them.

The eggs contained disembodied merfolk voices singing a song to the champions, letting them know that they had to come to lake and rescue something very valuable to them, which turned out to be a person very close to each of the champions. As the voices were those of merfolk, they could only be understood underwater.