Ghouls

Ghoul
Powers and Abilities	Shapeshifting
Vulnerabilities	Decapitation Brain trauma
Appearance	Human; can appear as any person they have fed on, living or dead.
Episode(s)	4.19 Jump the Shark 6.10 Caged Heat 13.06 Tombstone

Ghoul Where does the word ghouls come from? Before it came to be applied to any random sicko or serial killer it went all the way back to the medieval Arabic ghul...it will dig up graves to eat the dead. – Alex Irvine, The Supernatural Book of Monsters, Spirits, Demons and Ghouls

Characteristics

I should have known. It was the fresh kills that threw me. Ghouls don't usually go after the living. See, you're just filthy scavengers, feeding off the dead — taking the form of the last corpse you choke down. – Sam Winchester, 4.19 Jump the Shark

Ghouls are creatures that traditionally feed on the the dead (mostly by drinking their prey's blood), though some have been known to feed on living humans. They can only be killed by decapitation or the destruction of their heads. They can shapeshift, appearing human by taking the form of the last person they ate. Ghouls are unaffected by silver or holy water.

Ghouls are also known to create complex tunnel systems underneath graveyards, allowing they to freely move from grave to grave and feast without raising too much suspicion from hunters.

Episodes

4.19 Jump the Shark

Two offspring of a ghoul killed by John Winchester lure Sam and Dean to their town in order to take revenge. They take on the forms of Adam and his mother Kate Milligan, an old "girlfriend" of John's. Both are killed by Dean: the Kate ghoul is decapitated by a shotgun blast and Dean bashes in the brains of the Adam ghoul.

6.10 Caged Heat

Crowley shoves two ghouls into a room with Dean. They attempt to feed on Dean but are killed when Sam arrives to help.

6.16 ...And Then There Were None

Bobby mentions there were ghouls and a ghoul-wraith smorgasbord along highway I-80.

9.20 Bloodlines

Ghouls are revealed to be one of the five monster families running Chicago. When it appears war may break out between the shapeshifter and werewolf families over the death of Sal Lassiter, Margo Lassiter asks Freddie Costa if the ghouls plan to back the Lassiters. Costa tells her there is some trepidation on their part over Margo's proposed leadership of the shapeshifters.

12.15 Somewhere Between Heaven and Hell

After back-to-back-to-back hunts, Dean returns to the Men of Letters Bunker covered in ghoul, wraith, and siren gore.

14.05 Nightmare Logic

On her first solo hunt, Maggie is sent by Sam to Claremore, Oklahoma, where a suspected ghoul has been reported on the grounds of the Rawling family private cemetery.

Ghouls in Lore

A ghoul is an undead supernatural being originating from Arabian folklore. A ghoul or ghūl (which translated from Arabic means "demon") is known to inhabit cemeteries or other types of burial grounds; in lore they are known for preying on young children, drinking blood, stealing coins, and most famously consuming the flesh of the dead. It's in eating the dead they are able to then assume the identity/form of the deceased. In some lore, ghouls are not dissimilar to zombies, being corpses re-animated by witches or demons that can be commanded. Like zombies, the typical method for dispatching a ghoul is to destroy their brains.