Witches and sorcerers in Malaysia can bring forth a vampiric demon through a magical ceremony that involves the body of a stillborn child or the corpse of a family member. If the demon is male, it is called a bâjang; the female of the species is called a LANGSUIR. If the caster is strong enough, he can bind the demon to him as a familiar that can be passed down through the generations. The witch will then keep their bâjang familiar in a specially constructed container called a tabong. It is made of bamboo that is sealed with leaves and locked with a magical charm. 

The person who possesses the bâjang must personally feed it a diet of milk and eggs or else it will turn on its owner and then start eating its favorite food — children.

The bâjang can shape-shift into three different forms: a cat, a weasel, or a large lizard. In its cat form, if its mews at a baby, the child will die.

The witch will oftentimes send its familiar out to do its bidding. When it is sent out to harm a person, the bâjang will inflict upon its intended victim a mysterious disease for which there is no cure. The person will grow weak, suffering from convulsions and fainting spells until he eventually dies.

There is no known way to destroy a bâjang, but there are charms that can be made or purchased to keep it at bay. Probably the best way to deal with it would be to deal with the witch who commands it.

Source: Clifford, Dictionary of the Malay Language, 121; Gimlette, Malay Poisons and Charm, 47; Hobart, People of Bali, 116-117; Winstedt, Malay Magician, 25