The vrykolakas is a harmful undead creature of Greek folklore. It is generally equated with the vampire of neighboring Slavic countries, but it eats flesh — particularly livers — rather than drinking blood, which puts it closer to the modern zombie or ghoul. The word derives from the Bulgarian vǎrkolak, which originally meant “werewolf.”
A person might become one after a sacrilegious life, excommunication, burial in unconsecrated ground, or eating the meat of a sheep wounded by a wolf. The body does not decay but swells to a drum-like form, ruddy-faced. At night it knocks on doors and calls out the names of those inside; if no one answers the first time it passes on, but whoever opens the door dies a few days later and becomes a vrykolakas in turn. Hence the superstition in some Greek villages that one should not answer until the second knock.
Since it grows stronger if left alone, the body had to be destroyed — according to some accounts only on Saturday, the one day it rests in its grave. The belief was still common in rural Greece during the Second World War. In the Great Famine of 1941–1942, when cemeteries overflowed and families had to bury their dead outside them, some beheaded their loved ones’ corpses to keep them from returning.