Origin: Malaysia
A Polong is an evil spirit that is controlled by a Malaysian witch doctor (or "Bomoh"). If you are its master, you can use it to torment your enemies with madness, sickness, and eventually death.
To summon a Polong, you put the blood of a murdered person into a bottle and use incantations and magic spells. After two weeks, you will hear a chirping noise or the sound of crying coming from the bottle. Then you cut your finger and allow the blood to drain into the bottle and feed the demon.
This binds the Polong to you, telling it that you are its master and it is your servant.
Nobody knows exactly what a Polong looks like. Some say it appears in the bottle as a naked woman around an inch tall. Others say that when it is let out of the bottle, it looks like an egg-shaped fiery ball.