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 behaviors is to squeeze their victims' hearts and suck their blood. In addition, it is implied that they can transform into a non-human form, which apparently consists of large claws (one of which was discovered as the brothers examined a dead body at a playground with its chest cracked open) and a fierce roar. The one Sam and Dean fought seemed to wear a hooded robe similar to the shtriga, although it is unknown how common this practice is.
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.
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 is set on fire and burnt.
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.