Lamia

Lamias are a kind of supernatural creatures that the Winchesters have come across. Little information has been given about them - as they are monsters rarely seen out of Greece.

A lamia appeared briefly in Weekend At Bobby's, as one of Dean and Sam Winchester's cases.

Characteristics
As most of the other creatures that appear in the series, they can look like normal women that seduce young human men. One of their features is that they squeeze their victims' hearts and suck their blood. In addition, as it is implied, they can transform into a non-human form, which apparently has large claws (as the brothers examinated a dead body at a playground with its chest cracked open, and found a claw) and fiercely roar when they are in this form.

Known Abilities
Their abilities are vague, as they have only appeared once in Supernatural, in the episode Weekend At Bobby's, in which it is implied that Lamias have enhanced strength and agility, or at least, enough to overpower Sam and throw him in the air.

Weaknesses
Information about them says that there are two methods to kill a Lamia - one of them being the use of a silver knife blessed by a curate or priest, while the other is preparing a mixture of rosemary and salt, which is then thrown onto the Lamia. After doing so, the Lamia set on fire and burnt.

Mythology
In ancient Greek mythology, Lamia (Greek: Λάμια) was a beautiful queen of Libya who became a child-eating daemon. According to Diodorus Siculus, Lamia had an affair with Zeus and bore him children. When Hera, Zeus' wife, discovered the affair, she became enraged and killed the children. Driven insane with grief, Lamia began devouring other children, and, as related by Diodorus, her face became hideously distorted from her grisly deeds.

Later traditions referred to many lamiae; these were folkloric monsters similar to vampires and succubi that seduced young men and then fed on their blood.

Trivia

 * A sort of in-joke is played in Weekend At Bobby's, as Marcy Ward says that Bobby should come over and watch Drag Me to Hell. The Lamia is the antagonist of that movie.