Lamias are a rare, all-female species that is half snake (bottom) and half human (top), some also appearing to have wings. It has been debated whether they are mere monsters, phantoms, witches, or some sub-genre of demon. They have been known to drink the blood of young men and women and are cursed to devour the stillborns of both their own and other species.

Abilities/Powers: They can shapeshift to either become fully snake or fully human. They have fangs (two top, canines) that they can retract and claws that secrete a dangerous poison, the cure for which lamias have kept secret for millennia. They are the original founders and practitioners of blood magic, able to use the blood to both control and kill others, as well as become stronger and more deadly after consuming blood. They are also known for their gift of prophecy, however the strength of this ability varies from lamia to lamia. They have superhuman strength, speed, durability, and senses. Lamias have also been known to drive mortals to madness when exposed to their true forms and after holding eye contact for too long. 

Weaknesses: Lamias are weak against blessed silver, which poisons them (regular silver will merely irritate them). Hunters have found that using a combination rosemary and salt stuns lamias and leaves them susceptible to fire.

Societal/Political Stuffs: Lamias are typically anti-social creatures that settle in relatively quiet places such as small towns, abandoned places of worship, or isolated cabins. They don't have much allegiance to their species and some have even been known to specifically kill other lamias.

Mating: Since lamias are a purely female species, they look to other species to mate with, typically humans. Lamias are incredibly fertile, however whilst pregnant they will be either incredible pacified or consumed by bloodlust. Most lamias produce eggs in which their offspring will hatch from, however there are cases of lamias giving birth to live young, especially if they end up getting stuck in their human form. After the hatching/birth of their children, they will often abandon their mate, as lamias don't mate for life and very rarely enter into marriages or long-term relationships.

Offspring: Lamia offspring is purely dependent on the gender of the offspring. Females will become lamias while males will be whatever the father's species is. Male offspring, however, still carry the potential to sire lamias, as lamia blood is incredibly strong and no matter how long it takes, a female will become a lamia (there has been cases of males cursing their bloodline to only have male children in order to prevent the birth of a lamia). Lamias typically care for their children up until the age of their maturity before politely kicking them out of the proverbial nest or abandoning them, however this is more in the case of female offspring. Lamias will tend to leave their male offspring with the father before abandoning them both after the male offspring reach the age of maturity.

Life Cycle: Lamias go through childhood extremely quickly, taking about thirteen years to mentally, emotionally, and physically mature. They have incredibly long lifespans, as the first lamia is still alive today even after being born approximately 1st century BC. They do not expire naturally, only dying as the result of being killed or wounded to the point of death or by a poison stronger than their own.

Natural Enemies: Hunters (for obvious reasons) and themselves (for obvious reasons). 

Similar Creatures: Nagas and gorgons are certainly what come to mind, however there are differences. Nagas have the body of a snake and the head of a human and can be either male or female. Gorgons are typically humanoid with snakes attached to their scalp and the ability to turn those that view them to stone, many of which are female but there have been occasional sightings/stories of male gorgons.