a dog falls in a hole that emits mournful sounds

Taran is an assistant pigkeeper with boyish dreams of becoming a great warrior. However, he has to put the daydreaming aside when his charge, an oracular pig named Hen Wen, is kidnapped by an evil lord known as the Horned King. The villain hopes Hen will show him the way to The Black Cauldron, which has the power to create a giant army of unstoppable soldiers.