Actually, there was a trial, her three servants, who assisted in the torturing, were themselves tortured and had plenty to say., though, of course, she was not present.
They were executed.
The Countess, however, was walled up in her room (or suite of rooms) in the castle where she had caused such suffering to others.
Food was passed to her through a hole in the masonry.
One day, after years of this dark, solitary confinement, the food dish was not taken.
She had finally died.
I have not been able to find a picture or location of her grave.....I do not know if they simply left her body there and sealed the wall completely.
Considering the times, and the people, it would not surprise me.
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Sylkat
Student Body President, Miskatonic University