The PCs have been traveling for a long time down the same stretch or round with no sign of anything suspicious. As they cross over to the next hill they see a gigantic splater of blood with a bleached dragons scull in the center of it. It the dragon skull's mouth is a tattered backpack with something wiggling inside of it.
Could be used for killing a certain animal...a prized animal. The bones must be carefully buried or disposed of lest a sorcerer get a hold of it. With the bones of the dead creature the sorcerer can kill the hunter.