Lamia

In ancient Greek folklore, Lamia was a shape-shifting monster that sucked blood and ate flesh, similar to stories of the succubus and vampire. Lamia, the daughter of Belus and Libya, was loved by Zeus and punished by Hera. Because Hera took Lamia's children away, Lamia took her revenge on the children of men and women, since she had no power over gods. Lamia became transformed into a class of demonic being in Greek lore, the lamiai. According to folk beliefs, the lamiai might be in the form of a beautiful woman, a snake with a woman's head, or a monster with deformed lower limbs and the power to take out her eyes.

(See also Striges )

Sources:

Lawson, John Cuthbert. Modern Greek Folklore and Ancient Greek Religion. 1910. Reprint, New Hyde Park, N.Y.: University Books, 1964.

lamia a mythical monster supposed to have the body of a woman, and to prey on human beings and suck the blood of children. The word is used in early translations of the Bible for Isaiah 34:15 (where the Authorized Version has ‘screech owl’, with marginal alternative ‘night monster’) and Lamentations 4:3 (where the Authorized Version has ‘sea monsters’ or ‘sea calves’). Lamia comes via Latin from Greek, denoting a carnivorous fish or mythical monster.

In Keats's poem of this name, the serpent Lamia is transformed into a beautiful woman and wins the love of Lycius. At their wedding feast in Corinth her real nature is recognized by the sage Apollonius: he challenges her by her name, and she reverts to her true form, vanishing with a shriek of anguish.