Vrykolakas were the true Greek vampires. It was believed that a person could become a vrykolakas by living an immoral life, being excommunicated, died a violent death, buried without proper church rites, or being buried in unconsecrated ground. It was also thought that if you ate sheep that had been previously wounded by a werewolf, you would become a vampire.
There are different stories about the vrykolakas. One of the oldest stories of the vrykolakas was written by the French botanist, Pitton de Tournefort. While on Mykonos in 1700, he heard of a man who had recently died and was still being reported walking around the town making a nuisance of himself. After various remedies failed, his body was disinterred and the heart removed and burned 9 days after burial. The troubles did not stop. The troubles ended in 1701, when the body was fully consumed in a fire.
It was thought that vrykolakas would knock on the door of villagers, calling the names of the residents. If the door was not answered, it would pass without harm, but if the door was answered, the resident would die and become a vrykolakas.
The creature becomes more and more powerful if left alone, but they still had to return to the grave to rest. When in the grave, the the townspeople would exhume the body, behead it, impale it, and cremate it, as soon as possible to prevent it from feeding on humans. In the cases where they thought a person would become a vampire, the body may be buried upside down so that it would dig further into the ground instead of out. A stake may also be secured above the corpse so that it would impale itself if it tried to escape.