B.S. love the potential light. They strive to be closest to lightbulbs, camera flashes, stars and potentially mirroring surfaces. If they feel observed on their way to the promising light source, they will violently flash at you. Even through your closed eyes you can see their light echoing. A settled B.S. knows that you cannot see it directly, but will start to glare at you if you do not look away from the lightsource- rendering the flashy circles behind your eyelids or on your open eyes longer lasting.
How to fight it
Not dangerous and everywhere. To fight them seriously, you have to erase every potential light source and this is suicide when the much more dangerous shadow monster class is around.gab