Morowa Dziewica is a female polish demon similar to a banshee or a Strzyga (Strig).
They're said to fly around at night as a bloody sheet or an old skeletal hag, looking around for cities to bring & spread diseases. She would control people's minds & command them to wander around, giving the plague to everyone they were to meet.
This monster seems to have caused so much terror in people, that they would go mad and do the most horrible things to their loved ones.

I really hope you enjoy this small Contest Entry i made.~^^

Sincerely, Silence!☆