Succubi were female demons who were thought to seduce men and drink their blood. The Greeks and Romans also believed in a male counterpart to the succubi, called an incubus, who did much the same to women (1st source). There were also accounts of incubi and succubi in Hebrew mythology, though they were also believed to have been descended from fallen angels (frost, brian j).
Today’s image of the “classic vampire” is based mostly off of Eastern European folklore. The folklore of Eastern Europe generally told that people became vampires after death, like modern day ghosts. Whether or not one returned as a vampire was dependent on the person’s actions while alive. Some people believed to become vampires after death were drunks, thieves, witches, murderers, and those excommunicated from the church (2nd source). Other beliefs stated that people could become vampires if they were the first in their village to die from an outbreak of disease. It was common at the time to use these myths as scapegoats, as it was easiest to blame the problems of their village on the dead. This was especially prevalent during plagues because the vampire myth could be used to make sense of things. Around this time, vampires were used as an explanation for much of what the people feared or didn’t understand (2nd