The vrykolakas, variant vorvolakas or vourdoulakas, is a harmful undead creature in Greek folklore. It has similarities to many different legendary creatures, but is generally equated with the vampire of the folklore of the neighbouring Slavic countries. While the two are very similar, blood-drinking is only marginally associated with the vrykolakas.
The Greeks traditionally believed that a person could become a vrykolakas after death due to a sacrilegious way of life, an excommunication, a burial in unconsecrated ground, or eating the meat of a sheep which had been wounded by a wolf or a werewolf. Some believed that a werewolf itself could become a powerful vampire after being killed, and would retain the wolf-like fangs, hairy palms, and glowing eyes it formerly possessed.
The bodies of vrykolakas have the same distinctive characteristics as the bodies of vampires in Balkan folklore. They do not decay; instead, they swell and may even attain a "drum-like" form, they have a ruddy complexion, and are, according to one account, "fresh and gorged with new blood". People with red hair and gray eyes at this time in history were thought to be vampires according to accounts near the region of modern Serbia. The activities of the vrykolakas are nearly always harmful, verging from merely leaving their grave and "roaming about", through engaging in poltergeist-like activity, and up to causing epidemics in the community. Among other things, the creature is believed to knock on the doors of houses and call out the name of the residents. If it gets no reply the first time, it will pass without causing any harm. If someone does answer the door, he or she will die a few days later and become another vrykolakas. For this reason, there is a superstition present in certain Greek villages that one should not answer a door until the second knock. Legends also say that the vrykolakas crushes or suffocates the sleeping by sitting on them, much like a mara or incubus — as does a vampire in Bulgarian folklore.
Since the vrykolakas becomes more and more powerful if left alone, legends state that one should destroy its body. According to some accounts, this can only be done on Saturday, which is the only day when the vrykolakas rests in its grave (the same as with Bulgarian vampire legend) This may be done in various ways, the most common being exorcising, impaling, beheading, cutting into pieces, and especially cremating the suspected corpse, so that it may be freed from living death and its victims may be safe.