I would like to share a story my mother witnessed, for it happened to my mother's aunt in the 60's. I don't really know how to define what happened and what really happened. I will be pleased to have your point of view and knowledge on this subject.
My mother's aunt ("Betty ") was living with her in laws, husband and her 14 children (!) in a house the couple bought when they got married. The children grew older and all got married in their early twenties. Two of Betty's children left for another town and the 12 others lived near her or with her in the house. This house didn't show any paranormal activity until one day, a black mark appeared on a wall. This mark was looking like the head of a horse. Not knowing what it was, Betty and her husband tried to paint over the mark, and scrape the plaster, but the mark would reappear days later.
Few months after the appearance of the mark, one of Betty's daughters suddenly got very ill, and died within few weeks. Two years later, another daughter died from another sudden sickness. A couple of years after the 2nd death, another child died,...This kept going on until 12 of Betty's children passed away in their twenties, due to different illnesses. Once the 12th child was buried, the mark disappeared. The two survivors were the ones that had left the town. After that the mark disappeared, nothing else happened, and the house still belongs to the family.
What do you think this mark could be?
Is it somehow responsible or related to these deaths? (It was not common at the time to have so many deaths in a family).