The asema is a blood-sucking sorcerer or witch in the South American country of Surinam. This tradition may be imported from Africa with the slaves.
It is usually pictured as an elderly person during the day, which leaves its skin at night and flies off in the form that appears to be a blue ball of light. It uses this shape to feed from people's vital energy and/or blood.
Popular forms of protection against the asema were garlic, eating herbs that would make one’s blood bitter, and scattering rice or sesame seeds outside one's door, which it had to pick up before it could enter.
When the sesame seeds or rice grains are mixed with the nails of a ground owl, the asema is still compelled to count the seeds or grains, but each time it inadvertently picks up an owl's nail it lets go off all the seeds or grains it had counted and is forced to start over again.