A once compassionate healing monk who has taken on too many sins and was driven mad.
As for characters, I had this idea of a monk that was very peaceful in life that found she possessed a special ability. She was able to absorb the evil in men's hearts and the insanity in their minds into her own body, thus healing them. The monk being of great mental discipline was able to absorb the pain and suffering of thousands of men, and burry them deep down inside his soul where she kept them at bay. But being human, she had her limit, and she being the only one that possessed this power, there was no way to know what her limit was. Eventually she healed one too many and finally was no longer able to keep the insanity, pain, suffering and evil under control and it consumed her.
Now she is a citizen of Ravenloft, a being of pure malice, hatred, and the very essence of Evil. She is constantly tortured by the memories of the thousands of atrocities which drove those she healed insane. Her life of healing and of peace is long, long forgotten. She now roams the lands, She is literally walking insanity.