|Season(s)||4, 6, 13|
Ghouls are an race of supernatural creatures that have been encountered by Hunters such as Sam and Dean Winchester. The first time Sam and Dean have encountered ghouls in this series was when they took on the form of their long-lost half-brother Adam Milligan and Adam's mother. They also appeared in season 6 in Caged Heat in which Crowley attempted to have Sam and Dean fed to a pair of Ghouls.
Ghouls are scavengers creatures that live in graveyards and traditionally feed on flesh and blood of the dead. At times ghouls will change their diet and will feed on living humans instead of the dead. Ghouls will also take the form of people they eat (dead or alive).
The only thing that can kill a Ghoul is decapitation or complete destruction of the head.